ifelse(test, yes, no)
ifelse returns a value with the same shape as
test which is filled with elements selected
from either yes or no
depending on whether the element of test
is TRUE or FALSE.
If yes or no are too short, their elements are recycled.if.x <- c(6:-4) sqrt(x)#- gives warning sqrt(ifelse(x >= 0, x, NA))# no warning ## Note: the following also gives the warning ! ifelse(x >= 0, sqrt(x), NA)