mean by col in r dplyr code example

Example 1: colwise dplyr

df <- data.frame(g = c(1, 1, 2), x = c(-1, 1, 3), y = c(-1, -4, -9))
df %>%
  group_by(g) %>%
  summarise(across(where(is.numeric), sum))
#> `summarise()` ungrouping output (override with `.groups` argument)
#> # A tibble: 2 x 3
#>       g     x     y
#>   <dbl> <dbl> <dbl>
#> 1     1     0    -5
#> 2     2     3    -9

Example 2: dplyr average columns

library(dplyr)
mutate(df, IVMean = rowMeans(select(., starts_with("IV")), na.rm = TRUE))