How to Recode Data Based on a Lookup Using R

This article describes how to recode a variable, such as a state question, into...

... a variable of regions based on a lookup table or variables:

Requirements

A lookup table or to and from variables from the same data set. In this example, we will use a pasted table (Create > Tables > Enter Data) called US.States:

Method 1 - mapvalues() function

1. On the Variables and Questions tab and right click on a row to insert your variable and select Insert Variable(s) > R Variable.

2. In the bottom of the window, give it a Question Name, something like New Groups.

3. Paste the below under R CODE:

plyr::mapvalues(`What state do you live in?`, from=US.States$State, to=US.States$Region, warn_missing=F)

• The above code uses the R library plyr's mapvalues function so we need to first load that.
• The question, What state do you live in?, is in backticks because the label has spaces.
• The state variable is then compared to the State field from the US.States table and returns the Region field.
• Note, if your data does not match a lookup category, it will return the original data that your are looking up.

4. Click the play button to run the code and review the results.

5. Click Add R Variable.

6. Change the Question Type to Pick One.

Method 2 - match() function

1. On the Variables and Questions tab and right click on a row to insert your variable and select Insert Variable(s) > R Variable.

2. In the bottom of the window, give it a Question Name, something like New Groups.

3. Paste the below under R CODE:

x = as.character(`What state do you live in?`)
lookup = US.States
m = match(x,lookup$State)
x[!is.na(m)] = lookup[m[!is.na(m)], "Region"]
x[is.na(m)] = "Outside of USA"
x

• The above code converts our state question into text values and defines it as x.
• We use the match function to compare the state data with the lookup table's State field. This returns an index number.
• Where x matches the lookup table, we recode it with the corresponding Region data.
• Anything that does not match, i.e. is NA, we recode as "Outside of USA".
• We then return the recoded x as the final result.

4. Click the play button to run the code and review the results.

5. Click Add R Variable.

6. Change the Question Type to Pick One.

See Also

How to Learn R

How to Work with Conditional R Formulas

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

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

How to Filter Raw Data Using R

How to Create Filters in Q