Mutating multiple columns in a data frame using dplyr

Question

I have the following data frame df:

  v1 v2 v3 v4
1  1  5  7  4
2  2  6 10  3

And I want to obtain the following data frame

Answer 1

We can use base R instead of using any extra packages like dplyr or data.table

We can use mapply to vectorize the operation for multiple vectors at the same time

n <- ncol(df)/2
mapply(`*`, df[1:n], df[(n + 1):ncol(df)])

#     v1 v2
#[1,]  7 20
#[2,] 20 18

We can merge (cbind) this dataframe to your original one then.

---

If you are interested in tidyverse solution the equivalent in purrr would be variants of map2

purrr::map2_df(df[1:n], df[(n + 1):ncol(df)], `*`)

# A tibble: 2 x 2
#     v1    v2
#   
#1     7    20
#2    20    18