How to Create Variables Across Data Files Using JavaScript

JavaScript Variables can be created for one data file using data from the other data file using Q.GetValue. The way that JavaScript variables work when being used in a data file with a One to many relationship with another data file is different from how JavaScript variables work elsewhere in Displayr. This is because the nature of a One to many relationship is that each observation in the individual-level database is related to multiple observations in the other database (e.g., one household may have made multiple purchases). Consequently, in these situations, JavaScript expressions that refer to variables in the situational database return an array (i.e., a list of values).

Requirements

A Displayr document with more than one data set connected by a data file relationship. See How to Create Data File Relationships for more information.

Method

1. In the Data Sources tree, hover over any variable, then click + > Custom Code > JavaScript > and select the appropriate variable set structure.

2. Paste the following code into the JavaScript Code editor:

var brand = Q.GetValue('brand', 'Transactions.sav');
brand.length != 0

This is interpreted as follows:

• Q.GetValue('brand', 'Transactions.sav') gets, for each observation in the individual-level database, the data in the variable called brand in the situational database (i.e., Transactions.sav). If your data file is loaded from the Displayr Cloud Drive, this will be a little different, for which see the section below.  
  As mentioned, this is an Array. For example, if the household had made four purchases, of brands 3, 2, 1, and 1, then [3,2,1,1] would be returned.
• var brand = assigns the array to a variable called brand. (A variable in this context is temporary and does not create a variable called brand in the Data Sources tree.)
• brand.length computes the length of the array stored in the variable called brand (i.e., the number of values separated by commas).
• brand.length != 0 returns a 1 if the length of the array contains at least one entry and a 0 otherwise (i.e., it is a logical expression, and true is shown as 1 and false as 0).

You will need to update 'brand' and 'Transactions.sav' in the first line of code with the appropriate variable Name and data set name from your project.

3. Click Calculate.

4. Update the variable Name and Label from the General tab under General.

6. Update the Labels as necessary under Data > Properties.

If Your Data File is Loaded from the Displayr Cloud Drive

When specifying the file name that your source data is stored in, and the data file has been loaded from the Displayr Cloud Drive, then note the following:

• If the file is stored in the root directory/folder of the Displayr Cloud Drive, then you need to make no changes.
• If the file is stored in a folder on your Displayr Cloud Drive, then you should include the folder name(s) with double \\ between the folder names and the last folder and file name.

  • Example 1 - single folder:

    'Folder Name\\Transactions.sav'

  • Example 2 - multiple folders:

    'Folder One Name\\Folder Two Name\\Folder N Name\\Transactions.sav'

Next

How to Use JavaScript in Displayr

JavaScript Fundamentals