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ExpressionScript - Presentazione

From LimeSurvey Manual

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Introduzione

Utilizzando il nuovo modulo ExpressionScript (EM), LimeSurvey supporta ora tipologie di branching, valutazione, convalida e personalizzazione più complesse. Il nuovo modulo sostituisce, lato backend, la modalità di sostituzione, Impostazione delle condizioni e Valutazione. Il trattamento dei dati è considerevolmente velocizzato perché elimina la necessità di frequenti accessi in lettura sul database. EM è stato sviluppato dal Dr. Thomas White (TMSWhite).


Definizioni principali

  1. Espressione: una qualsiasi stringa delimitata da parentesi graffe:
    • purché non sia presente dello "white space" tra il testo e le graffe di apertura e chiusura.
    • Il contenuto dell'espressione è valutato da EM, pertanto esso può contenere formule matematiche, funzioni e in generale processamenti complessi di stringhe e dati.
  2. Adattamento (Tailoring): Detto anche "piping" in lingua Inglese. Si tratta del processo che modifica il testo in base a condizioni:
    • SI può agire su tutti i 'campi sostituibili', sui dati dei partecipanti e delle risposte.
    • Anche l'accesso a domande, risposte e loro proprietà è semplificato.
  3. Equazione di Rilevanza : Si tratta di un nuovo attributo di domanda che controlla la visibilità di una domanda:
    • Se esiste una equazione di rilevanza, allora la domanda è mostrata solo se il valore dell'espressione risulta essere true.
    • Internamente, tutti i filtri di tipo array_filter e array_filter_exclude sono trattati come equazioni di rilevanza a livello di sottodomanda.
  4. SGQA è il modo in cui precedentemente erano denominate le variabili e sta per
    • Survey-Group-Question-Answer
    • I nomi di variabile SGQA sono stringhe simili a 123X5X382X971 e possono anche includere suffissi per le sottodomande.
    • Si tratta di nomi variabile specifici per i sottostanti codici S/Q/G/A contenuti nel database e per questa ragione devono essere spesso cambiati
  5. Tipo di domanda Equazione: si tratta di un nuovo tipo di domanda che permette di salvare il risultato di calcoli o i report sul database:
    • Assomiglia a una domanda standard ma il suo contenuto è salvato sul database anche se si è impostato il flag "Nascondere sempre questa domanda".
  6. Codice Domanda: si tratta del nome variabile da preferire in EM:
    • Può essere un nome descrittivo, indicante lo scopo della domanda, in modo da rendere più semplice la lettura delle logiche complesse.
    • Perché un codice domanda sia valido, non deve mai iniziare con un numero: se si intende numerare le domande, utilizzare codici come "q1", "q1a" o "g1q2".
    • I codici domanda diverranno nomi di variabile nel caso si esportino i dati su SPSS o R. Questo significa che, in caso si desideri utilizzarli per fare analisi statistiche, i codici domanda dovranno essere univoci.


Devo proprio utilizzare EM?

La risposta, in generale, è "no". Tuttavia questo dipende molto dalla complessità del sondaggio che devi creare.

Ad esempio, l'Editor delle condizioni fornisce alcune espressioni di base che si possono applicare alle domande del sondaggio; tuttavia, il suo ambito è limitato. Questa è la ragione per cui si utilizza EM: aumentare le possibilità di personalizzazione.


Si possono mescolare Condizioni ed Equazioni di rilevanza?

Sì. Si può utilizzare l'Editor delle Conditioni per alcune domande e le Equazioni di Rilevanza per altri.

Non è possibile utilizzare, nella stessa domanda, condizioni edd espressioni! Una volta che una condizione è impostata, essa sostituisce l'eventuale espressione presente nel campo dedicato all'equazione di rilevanza. oltre a ciò, non è più possibile modificare manualemnte l'Equazione di rilevanza.

Tuttavia, esiste comunque un modo per utilizzare contemporaneamente espressioni e condizioni nella stessa domanda: come spiegato prima, una condizione sostituisce il contenuto del campo contenente l'equazione di rilevanza; a questo punto, l'equazione generata può essere copiata in un editor di testo. Si può quindi cancellare la condizione dall'Editor delle condizioni e poi modificare la domanda aggiungendo alle espressioni che si desidera utilizzare le espressioni condizionali precedentemente generate e copiate.


Quando utilizzare le Condizioni e quando la Rilevanza?

La lista mostra vantaggi e svantaggi di ciascun approccio:

Style Pro Contro
Conditions 1. GUI per la creazione di condizioni semplici.
2. GUI ben documentata e compresa dal team di supporto
1. Consente solo confronti semplici e non funziona bene nel combinare le condizioni con "AND" e "OR".
2. Le condizioni a cascata funzionano in modo irregolare
3. Lento - è pesante a livello di database e può rallentare i sondaggi più lunghi.
4. Sono stati riscontrati problemi nel ricaricare le condizioni.
5. La GUI non si adatta bene quando ci sono dozzine, centinaia o migliaia di domande.
6. La conversione dei sondaggi cartacei potrebbe essere lenta poiché deve utilizzare nomi SGQA.
7. Di solito è necessario un programmatore per compilare il codice necessario per eseguire ramificazioni complesse.
Rilevanza 1. Supporta una logica molto complessa, comprese oltre 80 funzioni e operatori matematici / di stringa.
2. Supporto perfetto per la logica a cascata.
3. Veloce - nessuna chiamata aggiuntiva al database e supporto per sondaggi di oltre mille domande.
4. Nessun problema con la logica di ricaricamento poiché non richiede i codici SGQA.
5. Il Syntax-highlighting consente sondaggi con oltre mille domande.
6. Facile e veloce da usare per i gruppi che desiderano informatizzare indagini cartacee preesistenti.
7. Supporta facilmente interviste semi-strutturate e indagini epidemiologiche senza bisogno di un programmatore.
1. Nessuna GUI per condizioni semplici - utilizza invece l'evidenziazione della sintassi.


Help.png Nota:
  • Ti consigliamo di utilizzare quello che meglio si adatta alle tue esigenze.
  • Per una spiegazione più dettagliata delle caratteristiche di EM, si veda la pagina relativa a EM e le sue caratteristiche.

Guida introduttiva

il modo migliore per iniziare ad usare EM è:

  • installare l'ultima versione stabile del software da https://www.limesurvey.org/en/download.
  • Importare ed esplorare alcuni sondaggi di esempio.
  • Esplorare gli use case e gli how-to e gli esempi passo-passo.
  • Esplorare la documentazione di EM (questa pagina)
    • Unit Tests di espressioni isolate (avanzato)
      • mostra esemip di utilizzo di tutte le funzioni e gli operatori di EM e i risultati PHP e JavaScript;
      • si noti ce ci sono diverse funzioni che generano risultati diversi nelle versioni PHP e JavaScript versions, pertanto questa pagina consente di pianificare di conseguenza la logica EM.

Terminologia

These words are commonly used to describe the capabilities of the EM:

  • 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). You may find the Relevance fields in the question editor panel as well as in the question group editor panel. The later is used to 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 substitution (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 survey respondent 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. The equation results are computed and written to the database, even if you hide them on the page. Thus, they are used for hidden scoring calculations, navigation based upon complex equations, assessments, and reports that will be generated and stored within the database.


Relevance and Cascading Relevance

Every question type now has a Relevance option which controls whether the question is displayed or not. The EM processes each Relevance Equation in the order they 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 five 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}?


Group-level Relevance

ExpressionScript also supports group-level relevance. This makes it easier to implement looping. Say you want to collect information from up to 10 entities (such as products or people from 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 knowing 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.

To check such an example, import the following survey: Census survey example.

It can be observed in the below screenshot that Person 1 group is displayed (or relevant) if the respondent lives with at least another cohabitant:


Group-level relevance example screen.png


Tailoring/Piping

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

By Using these equations, you can do things such as:

  1. Conditionally show tailored messages to the respondents based on 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. Think of it as a Text display question type, 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 in public or private statistics.


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 that 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',
               ''
             )
           )
         )
       )
     )
   )
 )
)}

The ExpressionScript supports the following syntax:

  • All standard mathematical operators (e.g. +,-,*,/,!);
  • All standard comparison operators (e.g. <,<=,==,!=,>,>=, plus their equivalents: lt, le, eq, ne, gt, ge);
  • Parentheses (so you can group sub-expressions);
  • Conditional operators (e.g. &&,| | and their 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., the SGQA codes;
  • Pre-defined functions (there are already 80+, 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
Help.png 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. It also avoids unexpected results if you were expecting strings but got numbers instead (or vice versa).

Warning with mismatch number and string and alphabetical/numerical comparison

When you want to compare value with relative or equality comparisons, pay attention at mismatches. A value entered by user (or provided via answer code) can be used as number if it is clearly a number. If you surround one of the values with ", a text/string comparison will take place. If you want to compare as number, never surround a number with ".

For example Q0.NAOK > "50" is true if Q0.NAOK is a numeric question with 9 as value. This is because the operator > will assume it is an alphabetical comparison and not a numerical one.

To make sure that you compare integer values, you can use intval(Q0.NAOK) > 50. Just remember if Q0.NAOK is not a number (empty or a string), then intval(Q0.NAOK) === 0. To compare string values ("A" < "B") use strcmp directly : strcmp(Q0.NAOK,"B") or strcmp(Q0.NAOK,"A5").

Caution about using Assignment Operator (=)

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 should 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 "==").


Example assignment operator.png


Using assignment operator

The main reasons you may want to use the assignment operator are:

  • You need to set the default value via equation for a question that does not accept default values (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...


Important.png  Attention : The assignment is done only in PHP. This means that the value is not getting updated on the same page, but only when the user moves to the next page. Therefore, please pay attention when the assignment operator is used on the same page with other expressions.



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

Some examples:

  • 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 enabled, some parts of the expression manager system cannot be used:

  • starting a HTML tag in expression but ending in another expression;
  • using a complex expression within a URL.


Help.png Please note that XSS is enabled by default in any LimeSurvey installation.


Examples and workarounds:

  • {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 you 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") - similar to 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 making it possible to shuffle questions around without having to keep track of group or question numbers.

Important: It is safer to refer to variables that occur in the 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 display 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

If you use the 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 >=


It is recommended to clear your expression of HTML that appears within your expression. If you use the LimeSurvey HTML editor, click on the "Source" button (located in the upper left part of the editor) and delete all the characters that are not related to your expression (e.g.,

,
, and so on).

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, the corresponding question codes are QuestionCode_comment and QuestionCode_other, respectively.

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.shown} {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'}


Usage of NAOK

NAOK --> "Not Applicable" (NA) is alright (OK)


Using NAOK, means that all or some of the variables are irrelevant (e.g. "Not Applicable" (NA) is alright (OK)).

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 subquestion is hidden, the EM returns an empty string.

Without NAOK, if one question or one subquestion is hidden, the EM returns always an empty string (same to returning 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).

More information is provided in the Overriding Cascading Conditions subsection.


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

Quite often you want to evaluate all the parts of a question, such as counting how many subquestions have been answered or summing up 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.


"This" variable

The "this" variable is used exclusively within the "Whole question validation equation" and "Subquestion validation equation" options (the later is not possible from GUI). 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 "Subquestion validation equation" to (this > 3).


"Self" variable

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

  • self
  • self.suffix
  • self.sub-selector
  • self.sub-selector.suffix
  1. suffix is any of the normal qcode suffixes (e.g., NAOK, value, shown)
  1. sub-selector can be one of the following:
  • comments - only subquestions that are comments (e.g., 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 an 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)}


"That" variable

The "that" variable is like the "self" variable, but it allows you to 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, let's create a question 'q1', 'q' representing also 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 the EM) can validate whether the variables exist or not. This may seem confusing since you may see quite lengthy equations. However, if you edit the question, you will see the original equation using "self" and/or "that".

Help.png You should not use these variables if
  • you want to explicitly name each variable used in an equation, or
  • 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.

Access to functions

The 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 to 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)
listifop (New in 3.16.1 ) Return a 'glue'-separated list of the specified question property (retProp) from questions in the list which pass the criteria (cmpProp op value) string listifop(cmpProp, op, value, retProp, glue, sgqa1, sgqa2, ... sgqaN)
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)
Help.png Click here if you wish to find out more about planned (or being constrained) functions.

Create new expression functions with plugin (New in 4.0.0 )

If you need a new function that doesn't exist in core, you can create one with a plugin. Such a new function is created using the expressionManagerStart event.

ExpressionScript knows which variables are local

In order to properly build the JavaScript for a page, EM needs to know which variables are set on the page, and what their JavaScript ID is (e.g., for document.getElementById(x)). It must also 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 text {name}, you said you are {age} and that you have {numKids}.  The sum of ages of your first {min(numKids,5)} kids is {sumage}


To download the above survey example, click on the following link: Number of kids survey example.

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

ExpressionScript provides this functionality by surrounding each expression with a named <span> element. Every time a value changes, it recomputes the expression that should appear in that <span> element and regenerates the display. You can have dozens or even hundreds of such tailored expressions on the same page.


Syntax highlighting

To help with entering and validating expressions, the 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 is broken and the questions that rely on the respective expression will not be shown to the respondents.
blue text Sample function name meaning and allowable syntax It refers to function names or things that should be functions since they are followed by an open parenthesis. They are displayed 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 as the question you are currently editing is shown in cyan text (it can be updated in javascript). The tooltip shows its name (if you used INSERTANS:xxx) or its 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 shown.
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 shown.
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. 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 signs within the expression are 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 within red boxes. 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.


Help.png By tooltips, we refer to the popup message that is displayed when you hover over certain functions and variables.


Additional reading

ExpressionScript sample surveys

Use cases and how-tos

Step-by-step examples

Reference for Developers

RoadMap, status, ToDo List