Running a function on each three sets of columns - r

Question

In my dataframe, the three responses (yes, maybe, no) to a question are printed as three separate variables (a binary outcome of each possible response).
I want to combine the three binary responses into one variable, showing which response was selected.
The following piece of code does this:
data$var1 <- ifelse(data$var1.Yes, 0,
ifelse(data$var1.Maybe, 1,
ifelse(data$var1.No,2, NA)))
However, because I have many variables (e.g., var1, var2, var3, etc..), I want to pass a function or loop where the code runs for multiple variables whose column names include ascending numbers.
I thought of the following function:
fun <- function(i){
paste0("data$var", i) <- ifelse(paste0("data$var", i, ".Yes"), 0,
ifelse(paste0("data$var",i,".Maybe"), 1,
ifelse(paste0("data$var",i,".No"),2, NA)))
}
fun(1:3)
Unfortunately, this does not work. How can I apply this function to several variables at once?
dput(test)
structure(list(var1.Yes = c(0, 0, 1, 0, 1, 1, 1, 0, NA, 1),
var1.Maybe = c(1, 0, 0, 1, 0, 0, 0, 0, NA, 0),
var1.No= c(0, 1, 0, 0, 0, 0, 0, 1, NA, 1),
var2.Yes = c(0, 0, 1, NA, 1, 1, 1, 0, 0, 1),
var2.Maybe = c(0, 1, 1, NA, 0, 0, 0, 0, 0, 0),
var2.No= c(1, 0, 0, NA, 0, 0, 0, 1, 1, 0),
var3.Yes = c(0, 1, 0, 0, 0, 0, 0, NA, 0, 1),
var3.Maybe = c(0, 0, 0, 0, 1, 1, 1, NA, 1, 0),
class = "data.frame"))

Answer 1

You can loop through each three columns;
lapply(1:(ncol(test)/3), function(col) ifelse(test[,col*3-2], 0,
ifelse(test[,col*3-1], 1,
ifelse(col*3, 2, NA))))
# [[1]]
# [1] 1 2 0 1 0 0 0 2 NA 0
#
# [[2]]
# [1] 2 1 0 NA 0 0 0 2 2 0
#
# [[3]]
# [1] 2 0 2 2 1 1 1 NA 1 0
This can be merged with your data:
cbind(test, matrix(unlist(lapply_results), nrow = nrow(test)))
Data:
data.frame(
var1.Yes = c(0, 0, 1, 0, 1, 1, 1, 0, NA, 1),
var1.Maybe= c(1, 0, 0, 1, 0, 0, 0, 0, NA, 0),
var1.No = c(0, 1, 0, 0, 0, 0, 0, 1, NA, 1),
var2.Yes = c(0, 0, 1, NA, 1, 1, 1, 0, 0, 1),
var2.Maybe= c(0, 1, 1, NA, 0, 0, 0, 0, 0, 0),
var2.No = c(1, 0, 0, NA, 0, 0, 0, 1, 1, 0),
var3.Yes = c(0, 1, 0, 0, 0, 0, 0, NA, 0, 1),
var3.Maybe= c(0, 0, 0, 0, 1, 1, 1, NA, 1, 0),
var3.No = c(1, 0, 1, 1, 0, 0, 0, NA, 0, 0)) -> test