Variables

June 16, 2016

Variables are computable expressions that can be used to simplify validation and enabling conditions that use complex expressions. The content of a variable can be substituted into question text or static text to provide text that is more informative and dynamic. Also, calculated variables are included in the export data files.
 

To add a variable:

First Method

  1. Click on the down arrow next to the ADD QUESTION button.
  2. Select ADD VARIABLE.

      

Second Method

  1. Right click on the question tree to pull up the context menu.
  2. Click on Add variable after.

    

Variables will appear in the question tree with the fx-icon.
     

Every variable will have a name, a type and an expression. Note that the variables do not have enabling or validation conditions, but a variable may still be disabled if it is part of the disabled section or sub-section. In that case the value of the variable is C#’s null.

 

Specify variable name:

A variable name is a unique identifier for the variable. Use to the variable name to refer to the variable in enabling conditions, validation conditions, question text, static text, or in the expression of other variables.

 

Specify variable type:

Choose the data type that you expect the variable’s expression to evaluate to (ie numeric, true/false, text). The variable type drop down menu has five possible types to choose from:

    
 

  • Boolean: This type can only evaluate to true or false
  • Double: A numeric type. This type allows for numbers with decimal values (e.g. 2.5, 3.42)
  • Date/Time: Type for values that are date and/or time
  • Long Integer: Type for integer values. Unlike the double type, this type will only allow for whole numbers (e.g. 2, 42, 7329)
  • String: Type for text values

 

Specify the expression:

Add the expression that you want to be evaluated to compute the value of the variable.

 

Example 1:

We want to define a variable fullName that is a combination of a person’s first name (question firstName) and a person’s last name (question lastName). Here the variable would be a *String* type because the variable will be text.

 

Example 2:

We want to define a variable countMissingAssets to count the number of household assets where yes or no has not yet been filled in for categorical multi-select question (question hhAssets) that is in yes/no mode.Here the variable type would be Long Integer because we expect the number of items missing a response to be a whole number.

We can later to use it in a static text to the interviewer that will tell them how many assets they still have not filled out yes or not to.

 

Example 3:

We want to define a variable hhsize that will compute the household size. We intend to use this later in validation conditions in the household food consumption module to calculate the amount of food item that was consumed per capita.

Here the variable type would be Long Integer because we expect the household size to be whole number. hhroster is the name of the roster that the household members are listed in and name is the variable that contains the household member’s names. To get the household size, we are counting the number of non-empty names that are listed on the roster