Avoiding type conflicts with dplyr::case_when

问题

I am trying to use dplyr::case_when within dplyr::mutate to create a new variable where I set some values to missing and recode other values simultaneously.

However, if I try to set values to NA, I get an error saying that we cannot create the variable new because NAs are logical:

Error in mutate_impl(.data, dots) :
Evaluation error: must be type double, not logical.

Is there a way to set values to NA in a non-logical vector in a data frame using this?

library(dplyr)    

# Create data
df <- data.frame(old = 1:3)

# Create new variable
df <- df %>% dplyr::mutate(new = dplyr::case_when(old == 1 ~ 5,
                                                  old == 2 ~ NA,
                                                  TRUE ~ old))

# Desired output
c(5, NA, 3)

回答1:

As said in ?case_when:

All RHSs must evaluate to the same type of vector.

You actually have two possibilities:

1) Create new as a numeric vector

df <- df %>% mutate(new = case_when(old == 1 ~ 5,
                                    old == 2 ~ NA_real_,
                                    TRUE ~ as.numeric(old)))

Note that NA_real_ is the numeric version of NA, and that you must convert old to numeric because you created it as an integer in your original dataframe.

You get:

str(df)
# 'data.frame': 3 obs. of  2 variables:
# $ old: int  1 2 3
# $ new: num  5 NA 3

2) Create new as an integer vector

df <- df %>% mutate(new = case_when(old == 1 ~ 5L,
                                    old == 2 ~ NA_integer_,
                                    TRUE ~ old))

Here, 5L forces 5 into the integer type, and NA_integer_ is the integer version of NA.

So this time new is integer:

str(df)
# 'data.frame': 3 obs. of  2 variables:
# $ old: int  1 2 3
# $ new: int  5 NA 3

回答2:

Try this ?

df %>% dplyr::mutate(new = dplyr::case_when(.$old == 1 ~ 5,
                                                  .$old == 2 ~ NA_real_,
                                                  TRUE~.$old))

> df
  old new
1   1   5
2   2  NA
3   3   3

来源：https://stackoverflow.com/questions/44893933/avoiding-type-conflicts-with-dplyrcase-when