Gestionnaire d’expressions

Remarque: Cette fonction est uniquement disponible dans LimeSurvey 1.92 ou plus tard.

Démarrage rapide

Vue d'ensemble

Quand vous paramétrez vos enquêtes, vous avez souvent besoin de pouvoir spécifier:

1. Navigation/branchement - permet de modifier l'ordre dans lequel sont posées les questions en fonction de la réponse du sondé
2. Peaufiner - comment poser la question (en se référant aux réponses précédentes, ou en conjuguant les phrases de votre question en fonction du nombre ou du genre de votre sondé), ou comment générer des rapports personnalisés (comme des évaluations ou des conseils sur mesure).
3. Validation - être sûr que la question valide certains critères, comme des valeurs min et max, ou corresponde à un motif précis.

L'ExpressionScript (EM) procure une façon intuitive de spécifier la logique de toutes ces fonctionnalités. Presque tout ce que vous pouvez écrire comme équation mathématique standard est une expression valide, même en appelant des fonctions. EM procure l'accès à 70 fonctions et peut facilement être étendu pour en supporter d'avantage. Il vous permet également d’accéder à vos variables avec des noms de variables lisibles (plutôt qu'avec la notation SGQA).

Les sections suivantes montrent quelles sont les principales circonstances où l'ExpressionScript (EM) est utilisé

Filtre conditionnel (Contrôle de navigation/branchement)

Certaines enquêtes utilisent une logique "aller à" ("Goto Logic"), par exemple si vous répondez à la Question1 avec la réponse C, alors sautez à la Question5. Cette approche est très limitée, car il est très difficile de valider et de maintenir la cohérence si vous avez à ré-ordonner les questions. EM utilise une équation booléenne pour spécifier toutes les conditions sous lesquelles une question peut être valide. Si la question est pertinente, alors la question est posée, sinon elle n'est pas applicable et la valeur NULL est stockée dans la base. C'est similaire à ce qui peut être fait par l'intermédiaire de l'éditeur de conditions, mais EM vous permet de spécifier facilement des critères bien plus complexes et puissants (et vous permet d'utiliser des noms de variables plutôt que la notation SGQA)

Cette image montre une façon d'appréhender la logique de la pertinence pour un questionnaire. Il calcule l'Indice de Masse Corporelle. L'équation de la pertinence est indiquée dans les crochets juste après le nom de la variable (qui est en vert). Donc, la pertinence du poids (weight), des unités de poids (weight_units), de la taille (height) et des unités de taille (height_units) sont toutes à 1, cela signifie que ces questions sont toujours posées. Cependant, la pertinence pour l'IMC est {!is_empty(height) and !is_empty(weight)}, ce qui veut dire que l'IMC sera calculé seulement si le sujet entre une valeur à la fois pour la taille et le poids (évitant ainsi le risque de division par 0). De même la question de rapport est montré seulement si le sujet répond aux quatre questions (taille, unité de taille, poids, unités de poids).

La pertinence est affichée et modifiable aux endroits suivants :

Voir / Modifier l'équation de filtre conditionnel au niveau de la question

Cette équation calcule l'Indice de Masse Corporelle (IMC). Elle est posée uniquement si la personne entre d'abord sa taille et son poid

Ceci est l'écran d'édition pour la question sur l'IMC

Notez que vous n'avez pas à utiliser les parenthèses quand vous entrez une équation de pertinence

Voir / Modifier l'équation de filtre conditionnel au niveau du groupe

Ceci est une exemple de sondage de recensement ; La première page demande combien de personnes vivent avec vous et l'enregistre dans la variable "cohabs". Cette page est affichée seulement si vous avez plus d'un co-habitant (elle est donc affichée pour la deuxième personne qui cohabite avec vous), et également elle est affichée seulement si vous avez spécifié quelle est votre relation avec la première personne (p1_rel).

Comme vous pouvez le voir, le groupe aussi possède des critères de pertinence du niveau question, de telle façon que chaque question n’apparaît que lorsque vous avez répondu à la question précédente (e.g.{!is_empty(p1_sex)}). EM combine pour vous les équations de pertinence du niveau Groupe et Question pour vous. Les questions dans un groupe sont posées uniquement si le groupe dans son ensemble est pertinent. Ensuite, seul le sous-ensemble de questions du groupe qui sont pertinentes seront effectivement posées.

Voici l'écran pour éditer la pertinence de niveau groupe pour cette question.

Notez que vous n'avez pas à utiliser les parenthèses quand vous entrez une équation de pertinence

Modification conditionnelle

EM vous permet facilement de déterminer des conditions simples et complexes pour vos questions. Parfois vous avez juste besoin d'une simple substitution, comme quand vous dites , "Vous nous avez dit que vous aviez acheté [Produit]. Qu'avez vous particulièrement apprécié en lui ?". Parfois vous avez besoin d'une substitution conditionnelle comme "[M/Mme] [Nom], seriez vous prêt à remplir notre sondage ?. Dans ce cas vous voulez utiliser M ou Mme en fonction du sexe de la personne. D'autres fois vous avez besoin de substitutions encore plus complexes (basées par exemple sur un calcul mathématique). Em supporte tous ces types de customisations.

Equations Conditionnelles

L'exemple de l'Indice de Masse Corporelle montre la capacité à calculer l'IMC d'une personne même en la laissant entrer sa taille et son poids dans des unités métriques ou non métriques.

Ici weight_kg est {if(weight_units == 'kg', weight, weight * .453592)}. La fonction if( ) signifie que si le sujet a entré son poids en utilisant les kilogrammes alors cette valeur est utilisée, sinon la valeur entrée (qui est donc en livres) est multipliée par 0.453592 pour la convertir en kilogrammes. La variable height_m utilise une approche similaire pour calculer la taille de la personne en mètres, même si elle a été entrée en pouces.

IMC calcule la formule du poids comme {weight_kg / (height_m * height_m)}.

Enfin le rapport personnalise le message en rappelant à l'utilisateur ce qu'il a tapé. (Vous avez affirmé que vous mesurez 2 m et que vous pesez 70 kg)

Bien que n'étant pas bien illustré dans l'image ci-dessus, weight_status utilise les conditions si() imbriquées pour classer le poids de la personne de l'insuffisance pondérale à l'obésité sévère. Vous pouvez voir cette équation dans la vue "Montrer la logique"

Pour cette question vous pouvez voir deux choses dans la fenêtre d'édition :

1. les expressions de conditions prennent des parenthèses
2. les expressions peuvent s'étendre sur plusieurs lignes si, comme dans ce cas vous souhaitez rendre les conditions imbriquées plus faciles à lire

Questions adaptées, réponses et rapports

Remarque : l'adaptation dynamique peut ne pas fonctionner si les options de réponse sont disponibles dans des cases à cocher sur la même question. Ceci résulte du fait que l'adaptation insère une balise <span>qui n'est pas valide à l'intérieur de la sélection d'options.

Cet exemple montre le rapport d'IMC

Ici, la fenêtre d'édition pour la même question

Comme vous pouvez le voir, rien de ce qui est entre parenthèses n'est considéré comme une expression, et donc rien ne présente de surbrillance en fonction de la syntaxe (code de couleur). En cas de fautes de frappe (noms de variables ou fonctions mal orthographiés ou inconnus), EM montrerait une erreur, comme cela, en montrant que height_unit est un nom de variable non défini (c'est en fait height_units), et que rnd() est une fonction non définie (le bon nom de la fonction est ronde()). Dans les deux cas, les erreurs seraient entourées par une zone rouge pour les rendre plus facile à déceler et à corriger.

Vous pouvez également voir que vous pouvez rapidement créer des rapports complexes, comme une table des valeurs saisies ou des conseils personnalisés.

Rappelons que toutes les conditions d'adaptation doivent être entourées avec des parenthèses, ainsi LimeSurvey sait quelles sont les parties de la question en texte libre et lesquelles doivent être analysées à travers le gestionnaire d'expressions.

Validation

EM contrôle la façon dont la plupart des options avancées de question fonctionnent. Ceci contrôle des variables comme nombre de réponses min/max ; valeurs individuelles min/max ; somme des valeurs min/max; et vérifie que les valeurs entrées correspondent aux chaînes modèles spécifiées. Vous continuez à saisir ces options avancées de question comme d'habitude. Cependant, maintenant, n'importe quelle valeur dans l'un de ces champs est considérée comme une expression, de sorte que vous pouvez avoir des critères min/max avec des relations conditionnelles complexes avec d'autres questions.

Dans tous ces cas, puisque l'option avancée de question est toujours considérée comme une expression, vous n'avez pas à utiliser des parenthèses lors de la spécification.

Les pages Enquêtes-Échantillon illustrent par de nombreux exemples pratiques l'utilisation d'expressions pour les validations.

Introduction

LimeSurvey 1.92 et suivants utilise le nouveau module gestionnaire d'expressions (ExpressionScript : EM) qui permet à LimeSurvey de gérer des critères plus complexes d'évaluation, de branchement, de personnalisation. Il remplace la gestion en arrière-plan des conditions, des remplacements et des évaluations. Il permet également d'accélérer considérablement le traitement, car il élimine la plupart des lectures de base de données lors de l'exécution. EM a été développé par le Dr Thomas White (TMSWhite).

Cette page du wiki est la référence définitive pour la syntaxe et les fonctionnalités du gestionnaire d'expression (ExpressionScript).

Définitions clés

1. "'L'expression"': Tout ce qui a entouré par parenthèses
   • Tant qu'il n'y a pas d'espace blanc immédiatement après la parenthèse d'ouverture ou avant la parenthèse fermante
   • Le contenu des expressions est évalué par EM, de sorte qu'elles peuvent contenir des formules mathématiques, des fonctions, des chaînes complexes et des transformations de dates.
2. "'Le peaufinage"': parfois appelé "la tuyauterie", c'est le processus de modification conditionnelle de texte (piping, tayloring)
   • Vous avez accès à toutes les valeurs de "remplacement de champs", des jetons, et d'insertion (INSERTANS)
   • Vous avez également un accès plus facile à des questions, des réponses, et de leurs propriétés.
3. "Équation de pertinence"  : un nouvel attribut de contrôle de visibilté de la question
   • Si il y a une équation de pertinence, alors la question ne s'affiche que si la pertinence est évaluée à vrai.
   • En interne, toutes les commandes array_filter et array_filter_exclude relèvent mainteant du niveau sous-question
4. "'Le type de question équation"' : Un nouveau type de question qui permet d'économiser des calculs ou des rapports de la base de données
   • C'est comme une question standard, mais son contenu est enregistré dans la base de données, même si vous réglez "Toujours Masquer cette Question"
5. "'SGQA"": C'est la manière dont les variables sont nommées dans LimeSurvey <= 1.91+
   • Signifie Survey-Groupe-Question-Réponse
   • SGQA les noms de variables ressemblent à 123X5X382X971, et peuvent avoir des suffixes pour les sous-questions.
   • Les noms de ces variables sont spécifiques à la base de données de codes sous-jacente S/Q/G/U, donc ont souvent besoin d'être changés
6. "'Code de question": C'est la meilleure variable pour EM
   • Ce peut être un nom descriptif indiquant l'objet de la question, afin de faciliter la lecture dans une logique complexe
   • Bien que non requis pour être unique dans LS <= 1.91+, il doit être unique si vous souhaitez utiliser EM
   • Les codes de question valides ne doivent PAS commencer par un chiffre, de sorte que lors de l'utilisation du code de question pour numéroter vos questions, il suffit d'utiliser "t1", ou "q1a" ou "g1q2".
   • C'est ce qui devient le nom de la variable si vous exportez des données dans SPSS ou de R, donc si vous faites de l'analyse statistique, vous les avez probablement déjà rendus uniques.

Dois-je utiliser EM le gestionnaire d'équations ?

La Réponse courte est non (mais aussi oui).

EM est entièrement rétro-compatible avec les questionnaires existants. Donc, si vous êtes satisfait de la façon dont LimeSurvey traitait les conditions d'utilisation et les évaluations dans ses versions <= 1.91+, vous pouvez continuer à le faire.

Cependant, EM remplace complètement la façon interne dont LimeSurvey traite les conditions. Qouique vous puissiez toujours utiliser l'Éditeur de Conditions pour créer et gérer des conditions, LimeSurvey 1.92 va convertir l'équivalent de la Pertinence des Équations. Dans le cadre de la mise à niveau, LimeSurvey 1.92 va auto-convertir toutes les conditions en pertinence d'équations.

Cela devrait vous donner le meilleur des deux mondes - vous pouvez continuer à utiliser LimeSurvey comme vous en avez l'habitude mais allez regarder la pertinence d'équation équivalente, de sorte que vous pouvez migrer progressivement à lapertinence d'équations directement chaque fois que vous voyez l'ajustement.

Puis-je mélanger conditions et pertinence d'utilisation ?

Oui. Vous pouvez utiliser l'éditeur de conditions pour certaines questions, et l'éditeur de pertinence pour les autres. Les Conditions sont converties en pertinence lorsque vous enregistrez la question.

Remarque, nous supposons que si vous utilisez l'éditeur de conditions, c'est que vous voulez modifier une équation de pertinence saisie manuellement. Donc, si vous avez des conditions existantes et que souhaitez modifier manuellement la pertinence, s'il vous plaît supprimez d'abord les conditions pour cette question. Plus précisément, copiez la pertinence d'équation générée dans un éditeur de texte, utilisez le menu des conditions pour supprimer toutes les conditions de la question (ce qui va également supprimer la pertinence), puis éditez la question et collez l'équation de pertinence générée avec l'éditeur de texte dans le champ de pertinence pour la question (et enregistrez la question). Si il y a suffisamment de demandes pour la suppression des conditions sans la suppression de l'équation de pertinence générée, nous ajouterons un bloc de processus de conversion.

Comment devrais-je choisir entre les conditions et la pertinence ?

Voici une liste des avantages et des inconvénients de chaque méthode :

Méthode	Pour	Contre
Conditions	1. Interface sympa pour créer des conditions simples 2. Interface bien documentée et comprise par l"équipe support	1. Supporte uniquement des comparaisons simples et pas bien les conditions avec /AND/OR 2. Les conditions en cascade fonctionnent de façon aléatoire 3. Lent - appels intensifs à la base de données donc ralentit les longs questionnaires 4. Des problèmes ont été rapportés lors de recharge de conditions 5. L'interface ne s'ajuste pas bien quand il y a des douzaines, des centaines ou des milliers de questions 6. Peut être lent pour convertir des questionnaires papier car doit utiliser les noms SGQA 7. Oblige souvent le programmeur à personnaliser le code logique utilisé pour les branchements complexes
Pertinence	1. Supporte des expressions logiques très complexes avec plus de 80 fonctions et des opérateurs math et chaînes 2. Supporte parfaitement les conditions logiques en cascade 3. Rapide - pas d'appels à la base de données, donc supporte les questionnaires à plus de 1000 questions 4. Pas de problème pour recharger la logique depuis qu'il n'utilise plus les noms SGQA 5. Ajustement de la surbrillance syntaxique pour des questionnaires de plus de 1000 questions 6. Facile et rapide à utiliser pour ceux qui souhaitent numériser des questionnaires papier existants. 7. Supporte facilement les interviews semi-structurées et les questionnaires épidémiologiques sans avoir besoin d'un programmeur	1. Pas d'interface pour les conditions simples, utiliser la surbrillance syntaxique à la place 2. Nouveau, donc l'équipe support ne le maîtrise pas complètement pour le moment.

En résumé, si vous êtes satisfait de la façon dont LimeSurvey 1.91+ fonctionne, il n'y a pas de raison de changer ce que vous faites.

Quels sont les autres avantages de l'utilisation de EM ?

Here are some of the other reasons you might want to use EM.

1. Calculations - you can create any calculation you can think of:
   • You have access to all common mathematical operators and functions
   • You have access to 70+ mathematical, date, and string processing functions
   • It is fairly easy for developers to add new functions if users need them
2. Storing Calculations to Database
   • You can now compute simple and complex calculations and/or scale scores AND have them stored in the database without needing JavaScript.
   • You use the Equation question type to accomplish this.
3. Assessments
   • You can now create assessments or scale scores from any question type, not just the subset that used to be supported
   • You can use Tailoring to show running or total assessment scores anywhere needed - even on the same page
   • You have more control over the reports generated based upon those assessment scores
   • You can store assessment scores in the database without needing JavaScript
   • You can hide assessment scores without needing JavaScript or CSS
4. Replacement Fields
   • Instead of using {INSERTANS:SGQA}, you can just use the Question Code - this makes it easier to read and validate.
   • This also avoids the common need to edit questions to change the SGQA code to make everything work.
5. Tailoring - you can conditionally display text based upon other values
   • Use the appropriate title for a subject, like (e.g. "Hello [Mr./Mrs.] Smith")
   • Output gramatically correct sentences based when singular/plural matter:  (e.g. "You have 1 child" vs. "You have 2 children")
   • Appropriately conjugate verbs and decline nouns based upon subject's gender and plurality.
6. New Variable Attributes - you can access the following to do your tailoring:
   • (no suffix) -  an alias for qcode.code
   • .code - the selected response code for the question if it is relevant (otherwise blank), or the text value if it is not a coded question
   • .NAOK - same as .code, but can be part of calculations or lists even if irrelevant
   • .value - the assessment value for the question if it is relevant (otherwise blank), or the text value if it is not a coded question
   • .valueNAOK - same as .value, but can be part of calculations or lists even if irrelevant
   • .shown - the answer as displayed to the user (this is what {INSERTANS:xxx}  does)
   • .qid - the question ID
   • .gid - the group ID
   • .sgqa - the SGQA value for the question
   • .jsName - the correct javascript variable name for the question, regardless whether defined on this page or another
   • .qseq - the question sequence (starting from 0)
   • .gseq - the group sequence (starting from 0)
   • .mandatory - whether the question is mandatory (Y/N)
   • .question - the text of the question
   • .relevance - the relevance equation for the question
   • .grelevance - the relevance equation for the group
   • .relevanceStatus - whether or not the question is currently relevant (1 if true, 0 if false)
   • .type - the question type (the one character code)
7. Dynamic On-Page Changes
   • All Relevance, Calculation, and Tailoring works dynamically on a page - so changes in values instantly update the page
   • So, you have questions dynamically appear/disappear based upon whether they are relevant
   • Questions are also dynamically tailored based upon responses on the page, so you can see running totals, tailored sentences and customized reports.
8. New Data Entry Screen
   • In addition to using the current data-entry system, you can just use Survey-All-In-One.
   • This supports the on-page relevance and tailoring, so data entry clerks can quickly tab through and they will only have to enter the relevant responses
   • This can be critical if your data entry person needs to see the tailoring, which is also dynamic.
9. Eliminates the need for most custom JavaScript
   • EM easily supports complicated computations, scoring, tailoring and conditional logic.
   • Some things will still need JavaScript (like custom layouts and conditionally hiding question sub-elements), but your JavaScript can use the EM functions so that you can access questions by their Qcode instead of SGQA, and access any of the question properties listed above.

What are some other helpful new features enabled by EM?

Regardless of whether you continue to use the Conditions Editor or manually compose Relevance Equations, you get these additional benefits:

1. You can create more complex validation criteria
   • All of the advanced question attribute (like max_answers, min_num_value_n, max_num_value) can use Expressions.  So, you min/max criteria can be easily adjusted based upon prior responses, even if they are on the same page.
   • EM also handles all regular-expression-based validation, so you can robustly combine preg and equation-based question attributes.
2. Easy Re-ordering (or deleting) of Questions and Groups
   • Prior to version 1.92, you could not re-order questions or groups if LimeSurvey thought that such-re-ordering could break conditions in which they were used.  Similarly, you could not delete questions if any other questions depended upon them.
   • With EM's syntax highlighting, it is easy to see and validate whether you try to use questions before they are declared.  So, we now let you re-order or delete questions and groups whenever you like.  EM will update all of the syntax highlighting to show you potential errors.
   • The re-order questions view has been enhanced to help with such review.  It now shows the question's relevance equation and tailoring, so you can immediately see whether any variables become pink (meaning they are used before being declared).
3. The Question/Group Navigation Index is always available and accurate
   • Prior to version 1.92, these indexes were not available if there were complex conditions
   • With EM, we can guarantee that they are accurate.
   • Subjects can even jump back, to a prior question, change the answer, then jump forward (or submit)
     • When jumping forwards, EM will re-validate all of the intervening questions/groups.
     • If any questions become irrelevant, they will be NULLed in the database so that your data is internally consistent
     • If any questions become relevant or newly fail mandatory or validation rules, EM will stop on that page and force the user to answer those questions before jumping to their final destination.
4. Auto-conversion of Conditions to Relevance
   • When you upgrade your database, all existing surveys that have conditions will have relevance equations generated for them
   • Whenever you import a survey, relevance equations will be created as needed
   • Whenever you add, delete, or modify conditions, EM will generate the appropriate relevance equation.
5. Convenient Syntax Highlighting
   • When EM shows the relevance equation, it will show the Qcode, even if you entered an SGQA code, as we assume this will be easier to read.
   • All variables are color coded to show whether they were declared before or after the current question (or before or after the current group).  This lets you quickly detect and fix cases where you try to use variables for relevance (including array_filter), tailoring, or validation equations prior to declaring them.
   • In addition, if you hover your mouse over the color-coded variable, you will see the most important metadata about that question.   This includes the Group Sequence #, Question Sequence #, Qcode, Text of the question, and all available answer choices (if it is a question type with enumerated answer choices).
     • The list of answer choices uses this syntax:  'answers':{key:val, ... }.
     • key has the syntax 'scale~code' where scale is the answer scale (e.g. for dual scale), and code is the answer code.
     • val has the syntax 'value~shown' where value is the assessment value (if using assessments, otherwise code)(e.g. Qcode.value), and shown is the display value as seen by the subject (e.g. Qcode.shown)
     • This means that many surveys can use calculations without needing assessment mode.  If you have enumerated answer options  that are unique, non-decimal, and non-negative, you can simply do calculations on the Qcode.code values.
6. Easy review of entire survey logic and content
   • There is a new Show Survey Logic feature that lets you see everything about the survey (or group or question) on a single page.
   • It shows the Group, Question, Sub-Question, and Answer-level details for the selected scope (survey vs. group vs. question)
   • It also shows the relevance, subquestion-level relevance (for array_filter and array_filter_exclude), and generated validation equation (for preg and any validation rules like min/max sum/number of values), and all non-blank question attributes.
   • Everything is syntax-highlighted so that you can see potential syntax errors (like unbalanced parentheses or use of variables before they were declared)
   • The syntax-highligting supports rapid navigation and editing of the survey.
     • If you click on a variable name, it opens a browser window (or tab) that shows you that question and lets you edit it.
     • If you click on a group name, it opens a browser window (or tab) showing the group-reorder view so that you can easily move questions around.
     • All of the question attributes are also syntax highlighted.  This lets you set and see expressions within advanced question options (like basing the max/min number/sum of values on an expression)
   • The EM author used similar view (a little cleaner) to let his collaborating Epidemiologists and Institutional Review Board validate and authorize surveys with thousands of questions in highly branched and tailored structured interviews

How Backwards Compatible is EM with 1.91+?

LimeSurvey 1.92 is fully backwards-compatible with 1.91+ with one exception/caveat:  1.92 handles less-than / greater-than comparisons against empty values differently than 1.91+.

One of the LimeSurvey demo surveys uses a set of conditions that translates to this relevance equation:  {(age < 16) or (age == 20) or ... or (age == 80)}. In LimeSurvey 1.91+, (age < 16) is FALSE when there is no answer (the value is blank).  However, in LimeSurey 1.92, (age < 16) is TRUE when there is no answer, since both PHP and JavaScript treat blank as 0 in mathematical comparisons.  Thus, 1.91+ would hide that question when age was unanswered, but 1.92 would show it.  We went to great pains to prevent this, but since we needed to have the Expressions generate identical results in PHP and JavaScript, there was no way to make 1.92 treat "" < 16 as FALSE.  Fortunately, there is an easy work-around for this.  If you want (age < 16) to be FALSE, then use this expression instead: {(!is_empty(age) and age < 16)}.  You can use the new Survey Logic File view to quickly identify and fix any such comparisons in your survey.

Getting Started

The best way to get started with EM is to:

• Install the latest stable version from http://www.limesurvey.org/en/download
• Import and explore the sample surveys.
• Explore the use cases and HowTos and step-by-step examples.
• Explore the EM documentation (this page)
• Examine the built-in EM test suite
  • From any survey, under tools, select the EM option
  • Available Functions lists the 70+ functions and syntax
  • Unit Tests of Isolated Expressions
    • shows examples of using all EM functions and operators, and the PHP and JavaScript results
    • note there are few functions that generate different results in the PHP and JavaScript versions, so this page lets you plan your EM logic accordingly.

What Functionality does ExpressionScript Extend/Replace? (LimeSurvey <= 1.91+)

Conditions => Relevance

Conditions controlled which  questions are visible.  The general syntax was SGQA operator Value, like 111X2X3 == "Y".  Conditions could be ANDed or ORed together, but mixing ANDs and ORs was difficult.  The conditions themselves were stored in a separate table, and large portion of LimeSurvey's code was devoted to managing Conditions.  Because of extensive database access, processing large numbers of conditions could cause noticable performance problems.  Furthermore, once you had conditions assigned to questions or groups, you were often not allowed to re-order or delete them.

Assessments => Equations and  Micro-Tailoring

Assessments let users create scale scores from a collection of questions.  However, they could not dynamically change on the current page, and their values were not stored to the database.

Replacements => Micro-Tailoring

Users could tailor some messages and questions based  upon prior responses.  For example, a question might be, {TOKEN:FIRSTNAME}, you said {INSERTANS:111X3X4} was your favorite sport.  However, it was not possible to do conditional tailoring (like say "Mr." or "Mrs." depending upon the person's gender), or conjugate verbs or decline nouns without fancy JavaScript.  Authors could implement surveys that seemed to tailor questions, but it required separate questions for each permutation, and complex conditions to decide which questions to display.

Validation

Question could be validated with Regular expressions, or minimum/maximum values, or let an SGQA response serve as the minimum or maximum value.  However, validations could not be based upon calculations of other variables without fancy JavaScript.

Equations

Equations were not supported without fancy JavaScript.

Equation Question Type

Equations could not be saved to the database (e.g. the final score for an assessment) without fancy JavaScript.

How Will ExpressionScript Replace/Extend That Functionality?

The ExpressionScript is a new core module within LimeSurvey that makes it much easier to support the type of complex functionality that used to require custom JavaScript.  It is also replacing the way LimeSurvey currently manages Conditions and Assessments.

New Terminology When Referring to ExpressionScript (EM)

EM "thinks" of its functionality in the following terms:

• Relevance-based Branching - if a question is relevant, then ask it, otherwise don't (e.g. make it invisible, and mark it as NULL in the database).  There is a new Relevance field for all Question types, and also for each Group (so you can apply a set of conditions to an entire group without having to copy the same condition to each question, and/or combine group and question-level conditional logic).
• Tailoring - Once you know which questions should be asked, tailoring (sometimes called piping) specifies how the question should be asked. This lets you support not only simple subsitution (like {TOKEN:FIRSTNAME}), but also conjugation of verbs and declination of nouns based upon the gender or number of your subjects.  It also lets you change the message you deliver to a subject based upon whether they answered (or how they answered) other questions.
• Equations - EM adds a new question type called Equation which stores the result of an Expression.  These equations results are computed and written to the database, even if you hide them on the page.  Thus, they are useful for hidden scoring calculations, navigation based upon complex equations, assessments, and reports that should be generated and easily available within the database.

Relevance and Cascading Relevance

Every question type now has a Relevance option which controls whether the question is displayed.  EM processes each of the Relevance Equations in the order they should appear in the survey.  If the expression is true (or missing - to support legacy surveys), the question will be displayed. If it is not relevant, then the question will be hidden, and the value will be NULLed in the database.  If there are no relevant questions in a group, the entire group will be skipped.

Moreover, if any of the variables within an expression is irrelevant, then the expression always evaluates to false.  This enables Cascading Relevance so that you do not have to write very long Relevance equations for each question.

Say you have 5 questions Q1-Q5, and you only want to show Q2 if Q1 was answered, and Q3 if Q2 was answered, etc.  The relevance equations might be:

Question Code	Relevance	Question
Q1	1	What is your name?
Q2	Q1	{Q1}, how old are you?
Q3	Q2	So, you are {Q2} years old.  Are you married?
Q4	Q3 == "Y"	{Q1}, how long have you been married?
Q5	Q4	How many children do you have, {Q1}?

The relevance calculations also work in JavaScript - so you could put all the above questions on one page and it would still work as expected.  In fact, EM totally replaces how EM processes Survey vs. Group vs. Question-at-a-time survey formats.  They now all use the exactly same navigation engine so they work identically regardless of survey style.

As long as you are on the same page, any data you entered will still be there, just hidden.  So, if you enter some information, then choose an option that makes them irrelevant, then make them relevant again, your answers will still be available.  However, as soon as you move to a different page, all irrelevant responses will be lost to integrity of the dataset.

Group-Level Relevance

ExpressionScript also supports group-level relevance.  This makes it easier to implement looping.   Say you want to collect information about up to 10 entities (such a products or people in a household), where you first determine how many entities need follow-up (such as by asking how many people live in a household, or having people check which products they like from a long list).  After knowning how many entities need follow-up, you can use Group-level relevance like {count >= 1}, {count >=2}, ... {count >= 10} for each of the 10 groups of follow-up questions.  Within each group, you can have question-level conditional logic (e.g. gender or age-specific follow-up questions for each subject).  The question and group-level relevance equations are ANDed together to determine which should be shown.

Tailoring / Piping

Anything within curly braces is now treated as an Expression (with one exception described below).  Expressions have acccess to all of the LimeReplacementFields, all of the variables (via several aliases), all typical equation operators (mathematical, logical, and comparison), and dozens of functions (that even work dynamically on the client-side).

Using these equations, you can do things such as:

1. Conditionally show tailored messages to the respondants based upon prior responses
2. Create Assessments and show Assessment results (or conditionally branch or show messages) based upon those results, all without using the Assessments module itself
3. Conjugate verbs and decline nouns within questions, answers, and reports.
4. Show summaries of responses before the "Show your answers" page at the end of the survey

Equations

There is a new question type called  Equation.  It is like a Boilerplate questions, except that it stores the value of what is displayed in the database.  So, if the Equation Question text contains an Assessment computation, that value would be stored in the database in a variable that can be displayed within public or private statistics.

This solves a common request for storing Assessment scores within the database

Syntax

Anything contained within curly braces is now considered an Expression (with one exception:  there must be no leading or trailing whitespace - this is needed to ensure the ExpressionScript does not try to process embedded JavaScript).

Note, it is OK for expressions to span multiple lines, as long as there is no whitespace after the opening  curly brace or before the closing curly brace.  This is especially helpful for nested if() statements like this:

{if(is_empty(PFTotals),
 '',
 if(PFTotals >= -5 && PFTotals <= -4,
   'Very Soft',
   if(PFTotals >= -3 && PFTotals <= -2,
     'Soft',
     if(PFTotals == -1,
       'Somewhat Soft',
       if(PFTotals == 0,
         'Moderate',
         if(PFTotals == 1,
           'Somewhat Hard',
           if(PFTotals >= 2 && PFTotals <= 3,
             'Hard',
             if(PFTotals >= 4 && PFTotals <= 5,
               'Very Hard',
               ''
             )
           )
         )
       )
     )
   )
 )
)}

ExpressionScript supports the following syntax:

• All standard mathematical operators (e.g. +,-,*,/,!)
• All standard comparison operators (e.g. <,<=,==,!=,>,>=, plus these equivalents:  lt,le,eq,ne,gt,ge)
• Parentheses (so you can group sub-expressions)
• Conditional operators (e.g. &&,| | and these equivalents: and,or)
• Single and double-quoted strings (which can each embed strings with the other quote type)
• Comma operator (so can have a list of expressions and just return the final result)
• Assignment operator (=)
• Pre-defined variables (to refer to questions, question attributes, and responses) - e.g. all of the SGQA codes
• Pre-defined functions (there are already 70+, and it is easy to add more)

Operators

EM syntax follows normal operator precedence:

Level	Operator(s)	Description
1	()	parentheses for grouping or calling functions
2	! - +	unary operators: not, negation, unary-plus
3	* /	times, divide
4	+ -	plus, minus
5	< <= > >= lt le gt ge	relative comparisons
6	== != eq ne	equality comparisons
7	and	logical AND
8	or	logical OR
9	=	assignment operator
10	,	comma operator

Note, for consistency between JavaScript and PHP, the plus operator (+) does addition if both operands are numeric, but does concatenation if both parts are non-numeric strings.  However, we recommend using the join() function for concatenation, as that makes your intent more clear, and avoids unexpected results if you were expecting strings but got numbers instead (or vice versa).

Caution about using Assignment Operator (=)

Note, you should avoid using the assignment operators unless absolutely necessary, since they may cause unexpected side-effects.  For example, if you change the value of a previous response, the cascading relevance and validation logic between that question and the current question is not re-computed, so you could end up with internally inconsistent data (e.g. questions that stay answered but should have been NULLed, or questions that are skipped but should have been answered).  In general, if you want to assign a value to a variable, you sould create an Equation question type, and use an expression to set its value.  However, there are some rare times that people really need this operator, so we made it available.

To help caution you about this operator, it is shown in red font within the syntax equations (so that you don't confuse it with "==")

Using Assignment Operator

The main reasons you may want to use assignment are:

• You need to set the default value for a question that does not accept defaults via equation (such as list radio, where the user interface lets you pick one of the answer options, but does not let you enter an equation).  However, be careful, as LimeSurvey will not be able to validate that your equation generates one of the allowable answers for that question.
• You need to forcibly change the response to a previous question based upon a later response
• etc...

You can use all expression manager system for this purpose. It's better to use an Equation question type to this purpose.

Some example:

• Set answer to a short text question in lowercase : {QCODE=strtolower(QCODE.NAOK)}
• Set a default answer to an array question type at start of a survey : {Q1_SQ1=(is_empty(Q1_SQ1.NAOK),"A99",Q1_SQ1.NAOK)}
• Set a default answer to an array texts question type at start of a survey : {Q1_SQY1_SQX1 = (is_empty(Q1_SQY1_SQX1.NAOK),"Inserted answer", Q1_SQY1_SQX1.NAOK)}
• Set an answer with condition : {QCODE=if(YesNo="Y","A1","")}

XSS security

With XSS enable, some expression manager system can not be used :

• starting a HTML tag in expression but ending in another expression
• use a complex expression in URL.

Example and workaround

• {if( 1 ,"<strong>","")}information{if( 1 ,"</strong>","")} is broken with XSS security, here you can use {if(1,"<strong>information</strong>","information")}
• <a href="/script.php?value={if(QCODE == "Y","yes","no")}">next</a>, here you can use an equation question because using a complete question code is OK : <a href="/script.php?value={EQUATION.NAOK}">next</a>

Access to Variables

ExpressionScript provides read-only access to whichever variables we might need.  For backwards compatibility, it provides access to the following:

• TOKEN:xxx - the value of a TOKEN (e.g. TOKEN:FIRSTNAME, TOKEN:ATTRIBUTE_5) (Only for NOT anonymous survey).
• INSERTANS:SGQA - the display value of an answer (e.g. "Yes"). For ExpressionScript it's the same that using {QCODE.shown}.
• All {XXX} values used by templates.
• In question text, you can use {QID} replaced by the question id and {SGQ} replaced by the SGQA of the question

In addition, ExpressionScript lets you refer to variables by the Question Code (the 'title' column in the questions table within the database).  This is also the variable label used when you export your data to SPSS, R, or SAS.  For example, if you have questions about name, age, and gender, you could call those variables name, age, and gender instead of 12345X13X22, 12345X13X23, and  12345X13X24.  This makes equations easier for everyone to read and validate the logic, plus makes it possible to shuffle questions around without having to keep track of group or question numbers.

Important: It is only safe to refer to variables that occur in preceding pages or questions.

Furthermore, ExpressionScript lets you access many properties of the Question:

Syntax	Meaning	Example	Example Result
Qcode	an alias for Qcode.code	{implode(',',name,gender)}	'Tom','M'
Qcode.code	the selected response code for the question if it is relevant (otherwise blank), or the text value if it is not a coded question	{implode(',',name.code,gender.code)}	'Tom','M'
Qcode.NAOK	same as Qcode - see discussion of NAOK	{gender.NAOK}	'M'
Qcode.value	the assessment value for the question if it is relevant (otherwise blank), or the text value if it is not a coded question	{gender.value}	'1'
Qcode.valueNAOK	same as Qcode.value - see discussion about NAOK	{gender.valueNAOK}	'1'
Qcode.shown	the dispay value for the question	{implode(',',name.shown,gender.shown)}	'Tom','Male'
Qcode.question	the text of the question	{gender.question}	'What is your gender?'
Qcode.mandatory	whether the question is mandatory (Y/N)	{gender.mandatory}	'N'
Qcode.qid	the internal question number (not the sequential number)	{gender.qid}	337
Qcode.type	the question type	{gender.type}	'G'
Qcode.jsName	the correct javascript name for the question, regardless whether declared on or off this page	{gender.jsName}	'java1827X3X337'
Qcode.gid	the internal group number (not the sequential number)	{gender.gid}	3
Qcode.qseq	the sequential number of the question, starting from 0	{gender.qseq}	5
Qcode.gseq	the sequential number of the group, starting from 0	{gender.gseq}	1
Qcode.relevanceStatus	whether the question is currently relevant (0 or 1)	{gender.relevanceStatus}	1
Qcode.relevance	the question-level relevance equation	{gender.relevance}	'!is_empty(name)'
Qcode.grelevance	the  group-level relevance equation	{gender.grelevance}	'num_children >= 5'
Qcode.sgqa	the SGQA value for this question	{gender.sgqa}	'1827X3X337'

HTML editor issue

  This issue is fixed after 2.05 build 140803

If you use HTML editor, some characters are replaced by HTML entities.

• & by &amp;
• < by &lt;
• > by &gt;

If you use HTML editor you need to use :

• and for &
• lt for <
• le for <=
• gt for >
• ge for >=

Qcode Variable Naming

Here are the details of how to construct a Qcode (and access some properties) by question type.  In general, Qcodes are constructed as:

 QuestionCode . '_' . SubQuestionID . '_' . ScaleId

For comment and other, question code are QuestionCode_comment and QuestionCode_other

Type	Description	Code	SubQs	Answer Options	Scales	Answer Code	Answer Shown	Relevance
5	5 Point Choice Radio-Buttons	Q1		1-5		{Q1}	{Q1.shown}	{Q1==3}
B	Array (10 Point Choice) Radio-Buttons	Q2	L1-L6	1-10		{Q2_L2}	{Q2_L2.shown}	{Q2_L2==7}
A	Array (5 Point Choice) Radio-Buttons	Q3	1-5	1-5		{Q3_1}	{Q3_1.shown}	{Q3_1>=3}
1	Array (Flexible Labels) Dual Scale	Q4	sq1-sq5	0:a1-a3	1:b1-b3	{Q4_sq1_0}	{Q4_sq1_1.shown}	{Q4_sq1_1=='b2'}
H	Array (Flexible) - Column Format	Q5	1-5	s,m,t		{Q5_1}	{Q5_1.shown}	{Q5_1=='s'}
F	Array (Flexible) - Row Format	Q6	F1-F5	1-5		{Q6_F3}	{Q6_F3.shown}	{Q6_F3==4}
E	Array (Increase/Same/Decrease) Radio-Buttons	Q7	1-7	I,S,D		{Q7_4}	{Q7_4.shown}	{Q7_4=='D'}
:	Array (Multi Flexi) 1 To 10	Q8	ls1,todo,ls2	min,max,avg		{Q8_ls1_max}	{Q8_ls2_avg.shown}	{Q8_ls2_min==7}
;	Array (Multi Flexi) Text	Q9	hp,st,sw	1st,2nd,3rd		{Q9_hp_3rd}	{Q9_hp_3rd.shown}	{Q9_hp_3rd=='Peter'}
C	Array (Yes/Uncertain/No) Radio-Buttons	Q10	1-5	Y,N,U		{Q10_1}	{Q10_1.shown}	{Q10_3=='Y'}
X	Boilerplate Question	Q11					{Q11.shown}
D	Date	Q12				{Q12}	{Q12.shown}
*	Equation	Q13				{Q13}	{Q13.shown}	{Q13>5}
~124~	File Upload (records number of files uploaded)	Q14				{Q14}		{Q14>0}
G	Gender Drop-Down List	Q15		M,F		{Q15}	{Q15.shown}	{Q15=='M'}
U	Huge Free Text	Q16				{Q16}	{Q16.shown}	{strlen(Q16)>100}
I	Language Question	Q17				{Q17}	{Q17.shown}	{Q17=='en'}
!	List - Dropdown	Q18		1-5		{Q18}	{Q18.shown}	{Q18==3}
L	List Drop-Down/Radio-Button List	Q19		A-Z		{Q19}	{Q19.shown}	{Q19=='X'}
O	List With Comment Drop-Down/Radio-Button List + Textarea	Q20		A-F		{Q20},{Q20comment}	{Q20.shown}	{Q20=='B'}
T	Long Free Text	Q21				{Q21}	{Q21.shown}	{strstr(Q21,'hello')>0}
M	Multiple Choice Checkbox	Q22	A-F, other			{Q22_E}, {Q22_other}	{Q22_E.shown}, {Q22_other}	{Q22_E=='Y'}
P	Multiple Choice With Comments Checkbox + Text	Q23	A-F			{Q23_D}, {Q23_Dcomment}	{Q23_D.shown}	{!is_empty(Q23)}
K	Multiple Numerical Question	Q24	self,mom,dad			{Q24_self}	{Q24_self.shown}	{Q24_self>30}
Q	Multiple Short Text	Q25	A-F			{Q25_B}	{Q25_B.shown}	{substr(Q25_B,1,1)=='Q'}
N	Numerical Question Type	Q26				{Q26}	{Q26.shown}	{Q26 > 30}
R	Ranking Style	Q27	1-4			{Q27_1}	{Q27_1.shown}	{Q27_1==3}
S	Short Free Text	Q28				{Q28}	{Q28.shown}	{Q28=='mine'}
Y	Yes/No Radio-Buttons	Q29				{Q29}	{Q29.shown}	{Q29=='Y'}

The reserved 'this', 'self', and 'that' variables

Quite often, you want to evalute all parts of a question, such as counting how many subquestions have been answered, or summing the scores.  Other times, you want to process just certain rows or columns of a question (such as getting the row or column sums and storing them in the database).  These reserved variables make that process relatively painless.

The 'this' variable is used exclusively within the "Whole question validation equation" and "Sub-question validation equation" advanced question options.  It expands to the variable names of each of the cells within those questions.  So, if you want to make sure that each entry is greater than three, you would set the "Sub-question validation equation" to (this > 3).

The 'self' and 'that' variable are more powerful, and serve as macros which are expanded prior to processing equations.  The syntax choices are:

• self
• self.suffix
• self.sub-selector
• self.sub-selector.suffix

suffix is any of the normal qcode suffixes (e.g. NAOK, value, shown)

sub-selector is one of:

• comments - only subquestions that are comments (e.g. from multiple choice with comment and list with comment)
• nocomments - only subquestions that are not comments
• sq_X - where X is a row or column identifier.  Only subquestions matching pattern X are selected. Note that search is done on complete code identifier, then sq_X match and include subquestions nX, X, Xn (e.g. if you use sq_1, subquestions a1, 1a, 1, 11 or 001 was included). Put attention at dual scale question type where subquestions code are QCODE_SQCODE_1 and QCODE_SQCODE_1 and to ranking question type where subquestions code are QCODE_1,QCODE_2 ....

Examples:

• Has any part of a question been answered?  {count(self.NAOK)>0}
• What is the assessment score for this question?  {sum(self.value)}

You can also use these to get row and column totals.  Say you have a array of numbers with rows A-E and columns 1-5.

• What is the grand total?  {sum(self.NAOK)}
• What is the total of row B?  {sum(self.sq_B.NAOK)}
• What is the total of column 3? {sum(self.sq_3.NAOK)}

The 'that' variable is like the 'self' variable, but lets you refer to other questions.  Its syntax is:

• that.qname
• that.qname.suffix
• that.qname.sub-selector
• that.qname.sub-selector.suffix

qname is the question name without any subquestion extensions.  So, say you create a question 'q1', that is its qname

Examples:

• Has any part of question q1 been answered?  {count(that.q1.NAOK)>0}
• What is the assessment score for q2?  {sum(that.q2.NAOK)}
• What is the grand total of q3? {sum(that.q3.NAOK)}
• What is the total of row C in q4?  {sum(that.q4.sq_C.NAOK)}
• What is the total of column 2 in q4? {sum(that.q4.sq_2.NAOK)}

The 'self' and 'that' variables can be used in any relevance,  validation, or tailoring.

The one caveat is that when you use the Show Logic File feature, it will show you the expanded value of 'self' and 'that'.  This lets you see the actual equation that will be generated so that you (and ExpressionScript) can validate that the variables exist.  This may seem confusing since you may see quite lenghty equations.  However, if you edit the question, you will see the original equation using 'self' and/or 'that'

Also note that you should not use these variables if (a) you want to explicitly name each variable used in an equation, or (b) use variables that do not have subquestions (e.g. single response questions).  In those cases, prefixing a variable with 'that' is overkill, and you run the risk of getting unexpected results.

Usage of NAOK

When you put some variable from question in any equation : if this question (or subquestion) is hidden by condition : this disable all equation.

For example : count(Q1_SQ1,Q1_SQ2,Q1_SQ3,Q1_SQ4) give always an empty string if one subquestion of Q1 is filtered. To count the number of checked subquestion in such question can be count(Q1_SQ1.NAOK,Q1_SQ2.NAOK,Q1_SQ3.NAOK,Q1_SQ4.NAOK). If the sub question is hidden :Exprssion manager return an empty string.

Without NAOK : if one question or one subquestion is hidden : ExpressionScript return always an empty string, same to return false.

The .shown always use the NAOK system (empty string if hidden) but if you need the code of the answer : it's always a good idea to add .NAOK after the question code. Except if you need it and know what you do.

Another example and information is provided at Overriding Cascading Conditions

Access to Functions

ExpressionScript provides access to mathematical, string, and user-defined functions, as shown below.  It has PHP and JavaScript equivalents for these functions so that they work identically on server-side (PHP) and client-side (JavaScript).  It is easy to add new functions.

Implemented Functions

The following functions are currently available:

Function	Meaning	Syntax
abs	Absolute value	number abs(number)
acos	Arc cosine	number acos(number)
addslashes	Quote string with slashes	string addslashes(string)
asin	Arc sine	number asin(number)
atan	Arc tangent	number atan(number)
atan2	Arc tangent of two variables	number atan2(number, number)
ceil	Round fractions up	number ceil(number)
checkdate	Returns true(1) if it is a valid date in gregorian calendar	bool checkdate(month,day,year)
convert_value	Convert a numerical value using a inputTable and outputTable of numerical values	number convert_value(fValue, iStrict, sTranslateFromList, sTranslateToList)
cos	Cosine	number cos(number)
count	count the number of answered (non-blank)questions in the list	number count(arg1, arg12, ..., argN)
countif	Count the number of answered questions in the list equal the first argument	number countif(matches, arg1, arg2, ... argN)
countifop	Count the number of answered questions in the list which pass the criteria (arg op value)	number countifop(op, value, arg1, arg2, ... argN)
date	Format a local date/time	string date(format [, timestamp=time()])
exp	Calculates the exponent of e	number exp(number)
fixnum	Display numbers with comma as radix separator, if needed	string fixnum(number)
floor	Round fractions down	number floor(number)
gmdate	Format a GMT date/time	string gmdate(format [, timestamp=time()])
html_entity_decode	Convert all HTML entities to their applicable characters (always uses ENT_QUOTES and UTF-8)	string html_entity_decode(string)
htmlentities	Convert all applicable characters to HTML entities (always uses ENT_QUOTES and UTF-8)	string htmlentities(string)
expr_mgr_htmlspecialchars	Convert special characters to HTML entities (always uses ENT_QUOTES and UTF-8)	string htmlspecialchars(string)
expr_mgr_htmlspecialchars_decode	Convert special HTML entities back to characters (always uses ENT_QUOTES and UTF-8)	string htmlspecialchars_decode(string)
idate	Format a local time/date as integer	string idate(string [, timestamp=time()])
if	Excel-style if(test,result_if_true,result_if_false)	if(test,result_if_true,result_if_false)
implode	Join array elements with a string	string implode(glue,arg1,arg2,...,argN)
intval	Get the integer value of a variable	int intval(number [, base=10])
is_empty	Determine whether a variable is considered to be empty	bool is_empty(var)
is_float	Finds whether the type of a variable is float	bool is_float(var)
is_int	Find whether the type of a variable is integer	bool is_int(var)
is_nan	Finds whether a value is not a number	bool is_nan(var)
is_null	Finds whether a variable is NULL	bool is_null(var)
is_numeric	Finds whether a variable is a number or a numeric string	bool is_numeric(var)
is_string	Find whether the type of a variable is string	bool is_string(var)
join (New in 2.0 build 130129)	Join elements as a new string	join(arg1, arg2, ... argN)
list	Return comma-separated list of non-blank values	string list(arg1, arg2, ... argN)
log	The logarithm of number to base, if given, or the natural logarithm.	number log(number,base=e)
ltrim	Strip whitespace (or other characters) from the beginning of a string	string ltrim(string [, charlist])
max	Find highest value	number max(arg1, arg2, ... argN)
min	Find lowest value	number min(arg1, arg2, ... argN)
mktime	Get UNIX timestamp for a date (each of the 6 arguments are optional)	number mktime([hour [, minute [, second [, month [, day [, year ]]]]]])
modulo-function	The modulo function is not supported yet. You can use the floor() function instead	floor(x/y)==(x/y)
nl2br	Inserts HTML line breaks before all newlines in a string	string nl2br(string)
number_format	Format a number with grouped thousands	string number_format(number)
pi	Get value of pi	number pi()
pow	Exponential expression	number pow(base, exp)
quoted_printable_decode	Convert a quoted-printable string to an 8 bit string	string quoted_printable_decode(string)
quoted_printable_encode	Convert a 8 bit string to a quoted-printable string	string quoted_printable_encode(string)
quotemeta	Quote meta characters	string quotemeta(string)
rand	Generate a random integer, see this example	int rand() OR int rand(min, max)
regexMatch	compare a string to a regular expression	bool regexMatch(pattern,input)
round	Rounds a number to an optional precision	number round(val [, precision])
rtrim	Strip whitespace (or other characters) from the end of a string	string rtrim(string [, charlist])
sin	Sine	number sin(arg)
sprintf	Return a formatted string	string sprintf(format, arg1, arg2, ... argN)
sqrt	Square root	number sqrt(arg)
stddev	Calculate the Sample Standard Deviation for the list of numbers	number stddev(arg1, arg2, ... argN)
str_pad	Pad a string to a certain length with another string	string str_pad(input, pad_length [, pad_string])
str_repeat	Repeat a string	string str_repeat(input, multiplier)
str_replace	Replace all occurrences of the search string with the replacement string	string str_replace(search, replace, subject)
strcasecmp	Binary safe case-insensitive string comparison	int strcasecmp(str1, str2)
strcmp	Binary safe string comparison	int strcmp(str1, str2)
strip_tags	Strip HTML and PHP tags from a string	string strip_tags(str, allowable_tags)
stripos	Find position of first occurrence of a case-insensitive unicode string (starting by 0, return false if not found)	int stripos(haystack, needle [, offset=0])
stripslashes	Un-quotes a quoted string	string stripslashes(string)
stristr	Case-insensitive strstr	string stristr(haystack, needle [, before_needle=false])
strlen	Get string length	int strlen(string)
strpos	Find position of first occurrence of an unicode string (starting by 0, return false if not found)	int strpos(haystack, needle [ offset=0])
strrev	Reverse a string	string strrev(string)
strstr	Find first occurrence of a string	string strstr(haystack, needle[, before_needle=false])
strtolower	Make a string lowercase	string strtolower(string)
strtotime	Parse about any English textual datetime description into a Unix timestamp	int strtotime(string)
strtoupper	Make a string uppercase	string strtoupper(string)
substr	Return part of an unicode string	string substr(string, start [, length])
sum	Calculate the sum of values in an array	number sum(arg1, arg2, ... argN)
sumifop	Sum the values of answered questions in the list which pass the criteria (arg op value)	number sumifop(op, value, arg1, arg2, ... argN)
tan	Tangent	number tan(arg)
time	Return current UNIX timestamp	number time()
trim	Strip whitespace (or other characters) from the beginning and end of a string	string trim(string [, charlist])
ucwords	Uppercase the first character of each word in a string	string ucwords(string)
unique	Returns true if all non-empty responses are unique	boolean unique(arg1, ..., argN)

Functions that are Planned or Being Considered

Other functions that are planned (or being considered) but which are not implemented yet include the following.  Some of these are for backwards compatability with another survey tool.

Syntax	Meaning	Comments
e()	returns the value of e
formatDate(X,PAT)	return the string value of date X formatted according to Java data format pattern PAT
formatNumber(X,PAT)	return the string value of number X formatted according to Java number format pattern PAT
getAnsOption(X)	returns the text corresponding to the selected option for answer X	this is the same as X.shown
getAnsOption(X,Y)	returns the text corresponding to the option at index Y of node X
getRelevance(X)	returns the relevance equation for question X
getStartTime()	returns the date corresponding to the system time when the interview was started
getType(X)	returns the string name of the datatype - e.g. *NA* if isNA()
gotoFirst()	jumps to the first relevant set of questions - this violates the normal flow of the system
gotoNext()	jumps to the next set of relevant questions - this violates the normal flow of the system
gotoPrevious()	jumps to the previous set of relevant questions - this violates the normal flow of the system
isAsked(X)	returns true if the answer is neither *NA*, *INVALID*, nor *UNASKED*
isInvalid(X)	returns true if the answer is of type *INVALID*
isNA(X)	returns true if the answer is of type *NA*
isNotUnderstood(X)	returns true if the answer if of type *HUH*
isRefused(X)	returns true if the answer is of type *REFUSED*
isSpecial(X)	returns true if the answer is of type *UNASKED*, *NA*, *REFUSED*, *INVALID*, *UNKNOWN*, or *HUH*
isUnknown(X)	returns true if the answer is of type *UNKNOWN*
jumpTo(X)	jump to the group containing the named question -- this violates the normal flow of the system
jumpToFirstUnasked()	jump to the first unasked question thus bypassing previous answered questions this violates the normal flow of the system
lastIndexOf(X,Y)	returns the last index (base 0) of string Y in string X. Returns -1 if Y is not contained within X
list(X,...)	a string containing a comma separated list of the positive values with "and" separating the last two
mean(X,...)	returns the mean of a list of values
numAnsOptions(X)	returns the number of answer options that question X has
orlist(X,...)	a string containing a comma separated list of the positive values, with "or" separting the last two
parseDate(X,PAT)	returns the date value of string X parsed with Java date format pattern PAT
parseNumber(X,PAT)	returns the numerical value of string X parsed with Java number format pattern PAT
showAllResponsesExcept( questionList,attributeList,attributeTitleList)	questionList = pipe-delimited list of question identifiers; attributeList = pipe-delimited list of attributes (like question#, title, text, type - so you can decide what to show); attributeTitleList = pipe-delimited list of table headers, so can internationalize the report.
showTheseResponses( questionList,attributeList,attributeTitleList)	questionList = pipe-delimited list of question identifiers; attributeList = pipe-delimited list of attributes (like question#, title, text, type - so you can decide what to show); attributeTitleList = pipe-delimited list of table headers, so can internationalize the report.

ExpressionScript Knows Which Variables are Local

In order to properly build the JavaScript for page, ExpressionScript needs to know which variables are set on the page, and what their JavaScript ID is (e.g. for document.getElementById(x)).  It also must know which variables are set on other pages (so that it can ensure that the needed <input type='hidden' value='x'> fields are present and populated).

Cascading Conditions

If any of the variables are irrelevant, the whole equation will be irrelevant (false).  For example, in the following table, N/A means that one of the variables was not relevant

Operator	Example	a	b	Result
+ (unary)	+a	N/A		false
!	!a	N/A		false
== (or eq)	a == b	N/A	5	false
== (or eq)	a == b	N/A	0	false
== (or eq)	a == b	N/A	N/A	false
!= (or ne)	a != b	N/A	5	false
!= (or ne)	a != b	N/A	N/A	false
!= (or ne)	a != b	N/A	0	false
> (or gt)	a > b	N/A	5	false
>= (or ge)	a >= b	N/A	5	false
< (or lt)	a < b	N/A	5	false
<= (or le)	a <= b	N/A	5	false
and	a and b	N/A	5	false
and	a and b	N/A	N/A	false
or	a or b	N/A	N/A	false
or	a or b	N/A	5	false
+	a + b	N/A	5	false
*	a * b	N/A	5	false
/	a / b	5	N/A	false
()	(a)	N/A		false
(exp)	(a && b)	N/A	5	false
(exp) op (exp)	(b + b) > (a && b)	N/A	5	false
function	sum(a,b,b)	N/A	5	false
function	max(a,b)	N/A	5	false
function	min(a,b)	N/A	5	false
function	implode(', ',a,b,a,b)	N/A	5	false
function	if(a,a,b)	N/A	5	false
function	is_empty(a)	N/A		false
function	is_empty(a)	0 (or blank)		true
function	!is_empty(a)	N/A		false

Overriding Cascading Conditions

Say you want to show a running total of all relevant answers.  You might try to use the equation {sum(q1,q2,q3,...,qN)}.  However, this gets translated internally to LEMif(LEManyNA('q1','q2','q3',...,'qN'),,sum(LEMval('q1'),LEMval('q2'),LEMval('q3'),...,LEMval('qN'))).  So, if any of the values q1-qN are irrelevant, the equation will always return false.  In this case, the sum() will show 0 until all questions are answered.

To get around this, each variable can have a ".NAOK" suffix (meaning that Not Applicable is OK) added to it.  In such cases, the following behavior occurs.  Say you have a variable q1.NAOK

1. q1 is not added to the LEManyNA() clause
2. LEMval('q1') will  continue to check whether the response is relevant, and will return '' if it is not (so individual irrelevant responses will be ignored, but they will not void the entire expression).

So, the solution to the running total problem is to use the equation sum(q1.NAOK,q2.NAOK,q3.NAOK,...,qN.NAOK).

The use of the .NAOK suffix also lets authors design surveys that have several possible paths but then converge on common paths later.  For example, say subjects answer a survey in a way that is outside the normal range of responses.  The author could alert the subjects that they may not get valid results, and ask them whether they really want to  continue with the survey.  If they say Yes, then the rest of the questions will be shown.  The condition for the "rest of the questions" would check whether the initial responses were answered within the normal range OR whether the subject said Yes to the question that is only relevant if they answered outside the normal range.

How does ExpressionScript Support Conditional Micro-Tailoring?

Here is an example of micro-tailoring (where Question Type=='expr' means an Equation):

Question Code	Relevance	Question Type	Question
name	1	text	What is your name?
age	1	text	How old are you?
badage	!is_empty(age)	expr	{(age<16) or (age>80)}
agestop	badage	message	Sorry, {name}, you are too {if( (age<16),'young',if( (age>80),'old','middle-aged') ) } for this test.
kids	!badage	yesno	Do you have children?
parents	1	expr	{!badage && kids=='Y'}
numKids	parents	text	How many children do you have?
kid1	parents && numKids >= 1	text	How old is your first child?
kid2	parents && numKids >= 2	text	How old is your second child?
kid3	parents && numKids >= 3	text	How old is your third child?
kid4	parents && numKids >= 4	text	How old is your fourth child?
kid5	parents && numKids >= 5	text	How old is your fifth child?
sumage	1	expr	{sum(kid1.NAOK,kid2.NAOK,kid3.NAOK,kid4.NAOK,kid5.NAOK)}
report	parents	yesno	{name}, you said you are {age} and that you have {numKids}.  The sum of ages of your first {min(numKids,5)} kids is {sumage}

All of these questions can be on a single page (e.g. in the same group), and only the relevant questions will display.  Moreover, as you enter the ages of children, the sum() expression in the last question will dynamically update on the page.

ExpressionScript provides this functionality by surrounding each expression with a named element.  Every time a value changes, it recomputes the expression that should appear in that element and regenerates the display.  You can have dozens, or even hundreds, of such tailored expressions on the same page, and the page will re-display all of them in a single screen refresh.

Mapping of LimeSurvey 1.91+ to ExpressionScript Functionality

Old Feature	New Feature	Comments
Conditions	Relevance	You can use very complex conditional equations, and access a broader range of variables
Assessments	Equation	Any assessment scores can be re-structured into an Equation. This both ensures that the score is written to the database, and also lets you see dynamic changes to the score value on the current page
Replacements	ExpressionScript	The core engine takes the input string and treats everything within curly braces as an Expression - so it handles all historical replacements types.  To avoid messing up embedded JavaScript, ExpressionScript only processes content between curly braces as long as (a)  there is no leading or trailing whitespace within the curly braces - e.g. {expr} is an expression, but { expr}, {expr }, and { expr } are not expressions.  Furthermore, ExpressionScript does not process content within its own strings (e.g. {list('hi','there {braces}')} generates "hi there {braces}").  It also ignores escaped curly braces (e.g. \{this is not an expression\})
Validation	ExpressionScript	The plan is to take the current min/max Question Attributes and have ExpressionScript process them.  That way the min/max values can be expressions themselves

Syntax Highlighting

To help with entering and validating expressions, EM provides syntax highlighting with the following features:

Types and Meanings of Syntax Highlighting

Color	Sample	Meaning	Tooltip	Comments
tan background	Sample	the whole equation	none	Anything within curly braces that is recognized as an equation (e.g. there is no leading or trailing whitepace) will be color-coded with a tan background to help distinguish it from surrounding text
bold red text	Sample	An error	Some explanation on error	Can be an unknow variable or an error in function, .... Survey can be totally broken, this don't show to public user.
blue text	Sample	function name	meaning and allowable syntax	function names, or things that should be functions since they are followed by an opening parenthesis, are presented in bold blue text. Tooltips show the meaning and allowable syntax for the function.
grey text	Sample	string	none	single and double-quoted strings are shown in grey text
cyan text	Sample	variable set on the same page,	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on the same page to the current question is shown in cyan text, showning it can be updated in javascript. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
green text	Sample	variable set on a prior page	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on a prior page is shown in bold green text. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold pink text	Sample	variable set on a later page in general : empty at survey start, but can be filled with index or move previous	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on a prior page is shown in bold pink text. These are erorrs since the variable is being used before it is declareed. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold tan text	Sample	a lime replacement value	the value	Lime Replacement Strings (like {TOKEN:xxx}, {PRIVACY_MESSAGE}) are shown in bold tan text.
red text	Sample	assignment operator (=)	warning message	If you use one of the assignment operator (=) that operator will be displayed in red text. This is meant to help prevent accidental re-assignment of values when you really meant to check whether a == b instead of setting the value of a = b.
normal black text	Sample	punctuation	none	All other punctuation within the expression is shown as normal black text.
red-boxed text	a bold red line surrounds the error	syntax error	description of the error	Any detected syntax errors are shown by surrounding the error with a red box. The tooltip shows the error. Examples include unmatched parentheses, use of undefined functions, passing the wrong number of arguments to functions, poorly structured expressions (e.g. missing operators between variables), trying to assign a new value to a read-only variable, trying to assign values to non-variables, or using unsupported syntax. Note that the syntax error dectection system may only report one error in an expression even if there are multiple errors; however, if any errors are detected, at least one error will be shown.