help changing a mutate_at() code to across() code

tidyverse
1

Hello all,

A line of code I use nearly every time I open R is df %<% mutate_at(vars("variable1","variable 2", etc.),factor) to change multiple things into factors at once. Now however, I see that mutate_at is being replaced by across(). Only, I've tried at least half a dozen different ways to convert the old code into the format across uses, and I can't seem to get it to work. Does anyone know a solution?

2

The equivalent for your example would be something like this:

library(tidyverse)

# Subtract 1,000 from the selected columns
# Note that both the variable selection and the mutating function are 
#  inside across
mtcars %>% 
  mutate(across(c(mpg, hp), ~ . - 1000))

Some other examples:

# Operate only on numeric values
iris %>% 
  mutate(across(where(is.numeric), round))

# Get the standard deviation of all numeric columns and, 
#  separately (outside of across), a count of rows
iris %>% 
  summarise(across(where(is.numeric), sd), n = n())

See the colwise Vignette for many more examples.

3

This almost got me there, but I'm still having some trouble. Working with my data set and using the vignette, I was able to write a line that half works:
pubdata=pubdata %>% mutate(across(.cols = "Race", "Sex", .fns = factor))
This transforms the Race variable into a factor, but for some reason it doesn't do anything with the Sex variable. It also completely destroys the Race variable somehow:

'data.frame': 1225 obs. of 2 variables:
Race: Factor w/ 1 level "Sex": NA NA NA NA NA NA NA NA NA NA ...
Sex : int 2 2 2 1 2 1 1 1 2 2 ...

Going back to the vignette, I tried to tweak what they had near the bottom (in the "how to transform existing code") to this:
pubdata %>% mutate(across(c(pubdata, "Race","Sex")), factor)
But this doesn't work at all, and just returns an error:

Error: Problem with mutate() input ..1.
x Must subset columns with a valid subscript vector.
x Subscript has the wrong type `data.frame<
Race: factor<9f711>
Sex : integer

. i It must be numeric or character. i Input ..1isacross(c(pubdata, "Race", "Sex")). Run rlang::last_error()` to see where the error occurred

For reference, this is what the old code does, and is exactly what I'm trying to duplicate:

pubdata=pubdata %>% mutate_at(vars("Race", "Sex"),factor)
str(pubdata)
'data.frame': 1225 obs. of 2 variables:
Race: Factor w/ 4 levels "1","2","3","4": 2 2 1 1 1 1 1 1 1 1 ...
Sex : Factor w/ 2 levels "1","2": 2 2 2 1 2 1 1 1 2 2 ...

4

What if you change this:

pubdata %>% mutate(across(c(pubdata, "Race","Sex")), factor)

to this:

pubdata %>% mutate(across(c("Race","Sex")), factor)

pubdata is the name of the data frame, rather than a column of the data frame, which is causing the error. Also, you don't need quotation marks around the column names. The call will work without them as well.

5

Unfortunately that didn't work either, and returns a similar error:

Error: Problem with mutate() input ..2.
x Input ..2 must be a vector, not a function.
i Input ..2 is factor.

6

Sorry, I didn't look carefully enough at your code. Note the change in the location of the parentheses below:

pubdata %>% mutate(across(c("Race","Sex"), factor))
1 Like
7

That fixed it, thanks!!

8

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