Adding a prefix to certain column names

Question

I have a problem very similar to this one: Adding a prefix to column names. I want to add a prefix to the column name - the only difference is, that I dont want to add the prefix to every column I have. Here the same minimum, reproducible example as in the question mentioned above:

m2 <- cbind(1,1:4)
colnames(m2) <- c("x","Y")

Resulting in:

     x Y
[1,] 1 1
[2,] 1 2
[3,] 1 3
[4,] 1 4

The code for adding a prefix "Sub" to both columns would look like this (as suggested by the user A5C1D2H2I1M1N2O1R2T1):

colnames(m2) <- paste("Sub", colnames(m2), sep = "_")

Resulting in:

     Sub_x Sub_Y
[1,]     1     1
[2,]     1     2
[3,]     1     3
[4,]     1     4

How can I add a prefix "Sub" only to the first column? I tried the following:

colnames(m2[,1]) <- paste("Sub", colnames(m2[,1]), sep = "_")

Result of the code: No Warning, no error but no prefix as well. Any suggestions? Besides base r any suggestions using dplyr are appreciated as well. Please let me know if you need any further information. Thanks in advance.

Answer 1

Try this:

colnames(m2)[1] <- paste0("Sub", "_", colnames(m2)[1])
# or if you prefer paste
#colnames(m2)[1] <- paste("Sub", colnames(m2)[1], sep = "_")

Answer 2

With dplyr, you can do:

m2 %>%
 as.data.frame() %>%
 rename_at(1, ~ paste("Sub", ., sep = "_"))

  Sub_x Y
1     1 1
2     1 2
3     1 3
4     1 4

Answer 3

Also paste() accepts vectors so you could do:

colnames(m2) <- paste0(c("Sub_", ""), colnames(m2))