### Name: ifelse
### Title: Conditional Element Selection
### Aliases: ifelse
### Keywords: logic programming

### ** Examples

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)

## example of different return modes:
yes <- 1:3
no <- pi^(0:3)
typeof(ifelse(NA, yes, no))   # logical
typeof(ifelse(TRUE, yes, no)) # integer
typeof(ifelse(FALSE, yes, no))# double