How to Create and Use Filters

This article describes several ways to create filters in Q and how to use them in tables.

Requirements

• A variable to be used as a filter.

Methods

Tagging existing variables

Any variable in the Variables and Questions tab can be tagged as a filter variable by pressing the  button. Any non-missing, positive values (i.e., greater than 0) are included in the filter.

1. Select the Variables and Questions tab
2. Click the button the enable the filter:
   
   

Quick method

The most straightforward approach to creating a filter is to select the cells on a table that correspond to the filter you wish to create, and then right-click and select Create filter.

1. Select the table you want to create the filter from.
2. Select the cells that correspond to the filter you want to create. In this example, respondents are selected if they prefer Coke products and are under 30 years old:
   
3. Click the button in the toolbar
4. Change the name of the filter (if desired)
   
5. Uncheck the Apply filter to the current table box if you do not want to apply the filter to the current table.
6. Click OK.
   Note that when you create a filter using this method, it is automatically created as a Binary - Complicated Variable, and is found at the top of the Variables and Questions tab, where it can be edited (by right-clicking on it).

Binary - complicated variables

A filter can be created using any type of data using Create > Variables and Questions > Variable(s) > Binary - Complicated Variable. See Binary Variable or the relevant Online Training modules listed at the top-right of this page for more information.

1. From the toolbar, select Create > Variables and Questions > Variable(s) > Binary - Complicated Variable
2. Specify a logical expression. In this example, persons aged 30 and over were selected.
3. Specify a name for the filter variable.
   
4. Click OK.

To learn more about this method, please see: How to Create a Complicated Filter in Q

Quickly creating filters using an existing question

For example, if you want to partition your dataset into test & train samples, you would do the following:

1. From the toolbar, select Automate > Browse Online Libary > Filter > Filter for Train-Test Split
2. Specify the size of your training sample, in this case 70%
   
3. Click OK.

Logic variables

These variables use a short and easy-to-use syntax for creating variables. For example, each of the following lines describes a filter, and in many cases the same filter (i.e., illustrating that there are lots of different ways of creating a filter using logic).

 To create a logic variable:

1. From the toolbar, select Create > Variables and Questions > Variable(s) > Logic Formula
2. For example:

   useCoke
   useCoke(1)
   NOT useCoke(0)
   age(#1, #2, #3, #9)
   age([18 to 24], [25 to 29], [30 to 34], [65 or more])
   age(1-3, 9)
   age([18 to 24]-[30-34],[65 or more])
   age(#1-#3, #9)
   age(1-3) OR age(9)
   age <= 3 OR age = 9
   NOT age([35-44]-[60 to 64])
   age >= [55-64] AND {occupation = [Retired] OR gender = [Female]}

JavaScript

Any JavaScript Variable can be used as a filter.

Rules and QScripts

The Online Library (Automate > Browse Online Library > Filters) contains various QScripts and Rules for creating filters.

Applying filters

Once a filter has been created, it can be applied to any table using the Filter drop-down on the bottom-left of the screen. Each time you apply a filter to a table using a Filter Drop-down Menu at the bottom of the Tables/Outputs Tab, another filter drop-down will appear to its right so that you can easily apply further filters to the same table. For example:

There are two ways of seeing that a filter has been applied. First, the drop-down displays the name of the filter with a green background. Second, the description of the sample size at the base of the screen also shows whether or not a filter has been applied.

To remove a filter, go to the Filter drop-down and select Total sample or press .

Managing Filters

In larger projects, it can sometimes be tricky to change a filter across a large number of tables, particularly when the filter is only applied to some of the tables, or the filter is applied in a different position on different tables. The QScript Filtering - Change Filters on Selected Tables can help save a lot of time when changing filters in a large project.

Next

How to Read a Filtered Table

How to Create New Variables

How to Create a Complicated Filter in Q