Refer to the last column in R

just use ncol() to get the index of the last col

data[,ncol(data)]

To refer to last column:

colnames(data)[ncol(data)]

Take the first element of the reversed vector of column names:

rev(names(mtcars))[1]
[1] "carb"

Similarly, to get the last column, you can use

rev(mtcars)[1]