dplyr case_when throws error names' attribute [1] must be the same length as the vector [0]

Question

I am running the following case_when inside a dplyr chain:

open_flag = case_when (
  open_flag == 0 & (click_flag > 0 | mirror_flag > 0) ~ 1,
  TRUE ~ open
)

All variables above are of type int . However, I get back this message:

Caused by error in names(message) <- vtmp : ! 'names' attribute [1] must be the same length as the vector [0]

I have found this post ( dplyr::case_when() inexplicably returns names(message) <- `*vtmp*` error ) that identified the issue. I don't fully understand the issue, and so I failed to apply a solution for my case_when() above!

Note: I can solve the problem by using ifelse() , but I really wonder how to solve it for the case_when() statement!

Answer 1

I believe you need to correct TRUE ~ open to TRUE ~ open_flag :

ERROR:

d %>% 
  mutate(
    open_flag = case_when(
      open_flag == 0 & (click_flag > 0 | mirror_flag > 0) ~ 1,
      TRUE ~ open
    )
  )

Error in `mutate()`:
! Problem while computing `open_flag = case_when(...)`.
Caused by error in `` names(message) <- `*vtmp*` ``:
! 'names' attribute [1] must be the same length as the vector [0]
Run `rlang::last_error()` to see where the error occurred.

CORRECT:

d %>% 
  mutate(
    open_flag = case_when(
      open_flag == 0 & (click_flag > 0 | mirror_flag > 0) ~ 1,
      TRUE ~ open_flag
  )
)

  open_flag click_flag mirror_flag
1         0         -1           0
2         2          0           0
3         1          1           3

Input:

d <- data.frame(
  open_flag = c(0, 2, 0),
  click_flag = c(-1, 0, 1),
  mirror_flag = c(0, 0, 3)
)

Answer 2

I received this same error message and scratched my head for 15 minutes. It was due to trying to combine integer and numeric types. Here is a reproducible example.

It's not a very useful error message:(

library(tidyverse)

# sample data
df <- tibble(
  int_var  = 1:10,
  real_var = as.numeric(1:10),
  use_int  = c(rep(TRUE, 5), rep(FALSE, 5))
)

# error
df %>%
  mutate(
    new_var = case_when(
      use_int ~ int_var,
      TRUE    ~ real_var
    )
  )
#> Error in `mutate()`:
#> ! Problem while computing `new_var = case_when(use_int ~ int_var, TRUE ~
#>   real_var)`.
#> Caused by error in `` names(message) <- `*vtmp*` ``:
#> ! 'names' attribute [1] must be the same length as the vector [0]

# fixed
df %>%
  mutate(
    new_var = case_when(
      use_int ~ as.numeric(int_var),  # coerce to numeric
      TRUE    ~ real_var
    )
  )
#> # A tibble: 10 × 4
#>    int_var real_var use_int new_var
#>      <int>    <dbl> <lgl>     <dbl>
#>  1       1        1 TRUE          1
#>  2       2        2 TRUE          2
#>  3       3        3 TRUE          3
#>  4       4        4 TRUE          4
#>  5       5        5 TRUE          5
#>  6       6        6 FALSE         6
#>  7       7        7 FALSE         7
#>  8       8        8 FALSE         8
#>  9       9        9 FALSE         9
#> 10      10       10 FALSE        10

^{Created on 2022-08-03 by the reprex package (v2.0.1)}