How to use map from purrr with dplyr::mutate to create multiple new columns based on column pairs

Question

I have to following issue using R. In short I want to create multiple new columns in a data frame based on calculations of different column pairs in the data frame.

Answer 1

In case you like to consider a base R approach, here's how you could do it:

cbind(df, lapply(split.default(df, substr(names(df), 0,1)), rowSums))
#  a1 b1 c1 a2 b2 c2  a  b  c
#1  1  4 10  9  3 15 10  7 25
#2  2  5 11 10  4 16 12  9 27
#3  3  6 12 11  5 17 14 11 29
#4  4  7 13 12  6 18 16 13 31
#5  5  8 14 13  7 19 18 15 33

It splits the data column-wise into a list, based on the first letter of each column name (either a, b, or c).

If you have a large number of columns and need to differentiate between all characters except the numbers at the end of each column name, you could modify the approach to:

cbind(df, lapply(split.default(df, sub("\\d+$", "", names(df))), rowSums))