Deselecting a column by name

Question

Is there a way to select all columns of a data frame except a column that has a particular name.

It would be the analog of df[, -1], except using the column name instead of the index?

Answer 1

You can do this using vector subsetting. First, create a dummy data set:

R> dd = data.frame(A = 1:3, B = 1:3, C=1:3, D=1:3) 

Then use the ! operator to reverse the selection:

R> dd[ ,!(colnames(dd) == "A")]    B C D 1 1 1 1 2 2 2 2 3 3 3 3 

Alternatively, you could have:

• A slightly shorter version (courtesy of @Tomas):

  dd[ , names(dd) != "A"] 

• To cope with multiple columns (courtesy of @Tyler)

  dd[ ,!(colnames(dd) %in% c("A", "B"))] 

Answer 2

One could use the which() function to identify the column to be eliminated.

dd <- data.frame(A = 1:5, B = 1:5, C=1:5)  dd[, -which(names(dd) == "A")] 

or positively

dd[, which(names(dd) != "A")] 

However, if there is no column named "A", you would get a data frame with 0 columns and nrow(dd) rows. So it would be good to check for the existence of a column named "A".

if(any(names(dd) == "A")) {   dd[, which(names(dd) != "A")] }