How to Use R Code to Create a Filter Based on Single-Response Questions

Introduction

There are many ways in which you can create a filter in Displayr. In some more complex scenarios creating a filter may require basic coding. This article describes how to use simple R code to create a filter based on a single-response question. 

Requirements

• A data set containing at least one single-response variable.
• Understanding of common R conditional operators (below), see How to Work with Conditional R Formulas for more detail:
  

Method - Create an R filter variable

1. Hover over a variable in the Data Sets tree and click on the + that appears then Custom Code > R - Numeric.  A new numeric variable called newvariable will appear in the Data Sets tree. 
2. Change the Label and Name of the variable in the object inspector via Properties > GENERAL to the desired text (e.g., Filter_variable).
3. Check Usable as a filter.
   

Method - Create the R filter logic

1. Under Properties > R CODE of your filter variable, enter the R code matching your binary filter condition. If the condition is met, the variable will return a value of 1 (which will be used to filter your data). If the condition is not met, the variable will return a 0 value.
2. Note, instead of typing the variable name, you can select the variables you wish to include in your R code and drag them from the Data Sets tree into Properties > R CODE for your filter variable. 
3. With R you can reference either the variable name or the variable set name. In cases when a variable name contains spaces, the label needs to be wrapped using ` `. For example, if we have a variable called "Q1" with the label of "Q1. How old are you?", in R we can reference this as either Q1 or `Q1. How old are you?`.

Examples

Below are examples of using R code to create filters:

d1 response equals the 25 to 29 category - note if there is missing data in the variable use the %in% operator below:

d1 == "25 to 29"

d1 %in% c("25 to 29", "45 to 49")

Q1 response equals 1:

Q==1

Q1<5 | Q2==2

Q1 is greater than or equal to 25 AND less than or equal to 100:

Q1>=25 & Q1<=100

And here are the reverse of the above filter conditions using the ! operator.

Q1 response is not 1:

Q1!=1

Q1 is NOT less than 5 AND Q2 is NOT 2:

!(Q1<5 | Q2==2)

Q1 is NOT greater than or equal to 25 AND NOT less than or equal to 100:

!(Q1>=25 & Q1<=100)

See Also

How to Work with Conditional R Formulas

How to Create a New Variable Based on Other Variables using R

How to Create a Simple Filter

How to Create a Binary Filter from Selected Data

How to Tag a Variable as a Filter