How to convert column types in R tidyverse

Question

I'm trying to get comfortable with using the Tidyverse, but data type conversions are proving to be a barrier. I understand that automatically converting strings to factors is not ideal, but sometimes I would like to use factors, so some approach to easily converting desired character columns in a tibble to factors would be excellent. I prefer to read in excel files with the readxl package, but factors aren't a permitted column type! I can go through column by column after the fact, but that's really not efficient. I want either of these two following things to work:

1. Read in a file and simultaneously specify which columns should be read as factors:

    data <- read_excel(path = "myfile.xlsx", 
                       col_types=c(col2="factor", col5="factor)))
   

2. Or this function would be excellent for many reasons, but I can't figure out how it's supposed to work. The col_types function is very confusing to me:

    diamonds <- col_types(diamonds, 
                          cols=c(cut="factor", color="factor", clarity="factor"))
   

Thanks in advance!

Answer 1

read_excel uses Excel cell types to guess column types for use in R. I also agree with the opinion of read_excel that one should read the data and allow a limited set of column types. Then if the user wishes, type conversion can take place later.

There is no function called col_types. That is a parameter name for read_excel. The tidyverse way would be:

library(tidyverse)

(foo <- data_frame(x = letters[1:3], y = LETTERS[4:6], z=1:3))
#> # A tibble: 3 x 3
#>   x     y         z
#>   <chr> <chr> <int>
#> 1 a     D         1
#> 2 b     E         2
#> 3 c     F         3

foo %>% 
  mutate_at(vars(x, y), factor)
#> # A tibble: 3 x 3
#>   x     y         z
#>   <fct> <fct> <int>
#> 1 a     D         1
#> 2 b     E         2
#> 3 c     F         3