Working on existing variables dynamically in for-loop

General
4 
suppressPackageStartupMessages(library(purrr))

paste0("X",seq(1:6)) -> the_factors 

mk_frame <- function(X) {
  the_frame <- data.frame(matrix(1:20,
                                 ncol = 4,
                                 nrow = 5))
  colnames(the_frame) <- c("X_var", "Y_var", X, "iteration")
  the_frame$poly <- as.factor(X)
  return(the_frame)
}

map(the_factors,mk_frame) -> list_of_dat 

list_of_dat[[1]]
#>   X_var Y_var X1 iteration poly
#> 1     1     6 11        16   X1
#> 2     2     7 12        17   X1
#> 3     3     8 13        18   X1
#> 4     4     9 14        19   X1
#> 5     5    10 15        20   X1
list_of_dat[[2]]
#>   X_var Y_var X2 iteration poly
#> 1     1     6 11        16   X2
#> 2     2     7 12        17   X2
#> 3     3     8 13        18   X2
#> 4     4     9 14        19   X2
#> 5     5    10 15        20   X2

Created on 2020-09-12 by the reprex package (v0.3.0)