You can drop columns from an R dataframe without using any R function. You need to find the columns you want to keep and then use them to slice the dataframe.
Here is an example. I am using set difference to find the columns that I want to keep in the resulting dataframe.
df <- data.frame(x=c(10,20,30,40), y=c(1,2,3,4),z=c(11,12,13,14), w=c(11,22,33,44))
cols <- colnames(df)
cols_to_del = c("y", "w")
df <- df[setdiff(cols, cols_to_del)]
Now df will have just 2 columns: x and z.
1 10 11
2 20 12
3 30 13
4 40 14