library(tidyverse, warn.conflicts = TRUE)
#> Warning: package 'tidyverse' was built under R version 3.6.3
#> Warning: package 'ggplot2' was built under R version 3.6.3
#> Warning: package 'tidyr' was built under R version 3.6.3
#> Warning: package 'purrr' was built under R version 3.6.3
#> Warning: package 'dplyr' was built under R version 3.6.3
#> Warning: package 'stringr' was built under R version 3.6.3
#> Warning: package 'forcats' was built under R version 3.6.3
df <- tibble(x = 1:10, y = 11:20, z = rep(1:2, each = 5),a = runif(10))
df %>% mutate(across(c(x, a), ~ .x / y))
#> # A tibble: 10 x 4
#> x y z a
#> <dbl> <int> <int> <dbl>
#> 1 0.0909 11 1 0.0885
#> 2 0.167 12 1 0.0464
#> 3 0.231 13 1 0.0586
#> 4 0.286 14 1 0.0590
#> 5 0.333 15 1 0.0111
#> 6 0.375 16 2 0.0595
#> 7 0.412 17 2 0.0320
#> 8 0.444 18 2 0.0311
#> 9 0.474 19 2 0.0386
#> 10 0.5 20 2 0.0236
Created on 2020-08-01 by the reprex package (v0.3.0)
From the above example, I would like to divide columns x and a by y rowwise. The suggested method is on this page Click here But I have to use column names as an argument in across function. Is there any way, I can use column numbers instead of their names? I would appreciate if I can use the trick for all instances of across.
We can replace the unquoted name with column index
library(dplyr)
df %>%
mutate(across(c(1, 4), ~ .x / y))
# A tibble: 10 x 4
# x y z a
# <dbl> <int> <int> <dbl>
# 1 0.0909 11 1 0.0470
# 2 0.167 12 1 0.000267
# 3 0.231 13 1 0.0453
# 4 0.286 14 1 0.0327
# 5 0.333 15 1 0.0382
# 6 0.375 16 2 0.0453
# 7 0.412 17 2 0.0105
# 8 0.444 18 2 0.0329
# 9 0.474 19 2 0.0396
#10 0.5 20 2 0.0249