When should I use “which” for subsetting?

Question

It is a toy example.

 iris %>% 
  group_by(Species) %>% 
  summarise(max = Sepal.Width[Sepal.Length == max(Sepal.Length)])

 # A tibble: 3 x 2
  Specie         


        

Answer 1

The which removes the NA elements. If we need to get the same behavior as which where there are NAsuse another condition along with==`

iris %>% 
  group_by(Species) %>% 
  summarise(max = Sepal.Width[Sepal.Length == max(Sepal.Length, na.rm = TRUE) & 
                                   !is.na(Sepal.Length)])