I have a vector of different column names and I want to be able to loop over each of them to extract that column from a data.frame. For example, consider the data set mtcars
and some variable names stored in a character vector cols
. When I try to select a variable from mtcars
using a dynamic subset of cols
, nether of these work
cols <- c("mpg", "cyl", "am")
col <- cols[1]
col
# [1] "mpg"
mtcars$col
# NULL
mtcars$cols[1]
# NULL
how can I get these to return the same values as
mtcars$mpg
Furthermore how can I loop over all the columns in cols
to get the values in some sort of loop.
for(x in seq_along(cols)) {
value <- mtcars[ order(mtcars$cols[x]), ]
}