Mutate and case_when is giving NA's

问题

I'm getting NA returned when using dplyrs casewhen in the mutate function. I like casewhen because I don't have to use the long ifelse statements if I want to FALSE value to be the default of the original value. Is this not the point of using casewhen? This code results in the NAs.

mtcars %>% 
  as_tibble() %>% 
  mutate(vs = case_when(carb == 4 ~ +5))

I'd like to add 1 to vs column when values of carb are 4. Thanks.

回答1:

You need to define the TRUE argument to all the remaining conditions which do not satisfy any condition and give it the value which you like.

library(dplyr)
mtcars %>% 
  as_tibble() %>% 
  mutate(vs = case_when(carb == 4 ~ 5, 
                        TRUE ~ vs))

#     mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
#    <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
# 1  21       6  160    110  3.9   2.62  16.5     5     1     4     4
# 2  21       6  160    110  3.9   2.88  17.0     5     1     4     4
# 3  22.8     4  108     93  3.85  2.32  18.6     1     1     4     1
# 4  21.4     6  258    110  3.08  3.22  19.4     1     0     3     1
# 5  18.7     8  360    175  3.15  3.44  17.0     0     0     3     2
# 6  18.1     6  225    105  2.76  3.46  20.2     1     0     3     1
# 7  14.3     8  360    245  3.21  3.57  15.8     5     0     3     4
# 8  24.4     4  147.    62  3.69  3.19  20       1     0     4     2
# 9  22.8     4  141.    95  3.92  3.15  22.9     1     0     4     2
#10  19.2     6  168.   123  3.92  3.44  18.3     5     0     4     4
# ... with 22 more rows

来源：https://stackoverflow.com/questions/53794220/mutate-and-case-when-is-giving-nas