Conditional transformations (3)

x <- c(-3:3, NA)
case_when(
  x == 0   ~ "0",
  x < 0    ~ "-ve", 
  x > 0    ~ "+ve",
  is.na(x) ~ "???"
)

## [1] "-ve" "-ve" "-ve" "0"   "+ve" "+ve" "+ve" "???"