Get column index from label in a data frame
r
Solution
you can get the index via `grep` and `colnames`:
grep("B", colnames(df))
[1] 2
or use
grep("^B$", colnames(df))
[1] 2
to only get the columns called "B" without those who contain a B e.g. "ABC".
Problem
Say we have the following data frame: ``` > df A B C 1 1 2 3 2 4 5 6 3 7 8 9 ``` We can select column 'B' from its index: ``` > df[,2] [1] 2 5 8 ``` Is there a way to get the index (2) from the column label ('B')?