Problem converting columns from character to factor using across within mutate

Question

I am encountering a problem when I run the following code to try to convert several columns of data from character to factor:

library(readxl)
library(dplyr)

"LR_df1"<-read_excel("Correct file location.xlsx",sheet="Correct sheet")


LR_df1 %>%
  as_tibble()%>%
  mutate(across(c(SiteCode, S01UsualResidence), as.factor))

The initial output looks good, and it appears that the specified columns have been converted:

    # A tibble: 1,075 x 238
       A CaseId SiteCode S01Gender S01UsualResidence
   <dbl>  <dbl> <fct>    <chr>     <fct>

But then when I run:

summary(LR_df1$SiteCode)

I get:

> summary(LR_df1$SiteCode) Length Class Mode 1075 character character

So it appears that the variable hasn't been converted. I'd be very grateful to anyone who can show me what I'm doing wrong.

This is because you did not save your output back to `LR_df1`. — www, Jun 14 '22 at 12:46

score 1 · Answer 1 · answered Jun 14 '22 at 12:49

1

mutate(), like all other functions from dplyr, doesn't permanently change the dataframe it works on. On its own, it will output a changed dataframe, but the original dataframe stays intact.

If you want it to permanently change the dataframe, you need to reassign:

LR_df1 <- LR_df1 |> mutate(...)

answered Jun 14 '22 at 12:49

Andrea M

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Thank you. Just learning to use dplyr and this is very helpful! – donm79 Jun 14 '22 at 13:10

Problem converting columns from character to factor using across within mutate

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