Efficiently transform multiple columns of a data frame

Question

I have a data frame, and I want to transform all columns (say, take the logs or whatever) with columns that match a certain name. So in the example below, I want to take the

Answer 1

In the case of functions that will return a data.frame:

cols <- c("X.1","X.2")
df[cols] <- log(df[cols])

Otherwise you will need to use lapply or a loop over the columns. These solutions will be slower than the solution above, so only use them if you must.

df[cols] <- lapply(df[cols], function(x) c(NA,diff(x)))
for(col in cols) {
  df[col] <- c(NA,diff(df[col]))
}