rowwise_purrr.R

library(tidyverse)

iris %>%
  tibble::as_tibble(.) %>%
  dplyr::mutate(., row_mean = pmap_dbl(list(Sepal.Length, Sepal.Width), mean))
  
#> # A tibble: 150 x 6
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species row_mean
#>           <dbl>       <dbl>        <dbl>       <dbl> <fct>      <dbl>
#>  1          5.1         3.5          1.4         0.2 setosa       5.1
#>  2          4.9         3            1.4         0.2 setosa       4.9
#>  3          4.7         3.2          1.3         0.2 setosa       4.7
#>  4          4.6         3.1          1.5         0.2 setosa       4.6
#>  5          5           3.6          1.4         0.2 setosa       5  
#>  6          5.4         3.9          1.7         0.4 setosa       5.4
#>  7          4.6         3.4          1.4         0.3 setosa       4.6
#>  8          5           3.4          1.5         0.2 setosa       5  
#>  9          4.4         2.9          1.4         0.2 setosa       4.4
#> 10          4.9         3.1          1.5         0.1 setosa       4.9
#> # ... with 140 more rows