Let’s say I have a data frame called df and a vector that contains the column names:

df = data.frame(a = 1:10,b = 11:20,c = 21:30)
colnames = c('a','b','c')

Is there a way that is equivalent to doing df$a to call a specific column, but that would use the names stored in the object colnames ? Something like this:

df$colnames[1]