Skip to content

A question on function return

3 messages · Christofer Bogaso, Rui Barradas, Peter Ehlers

Original
Christofer Bogaso
# 
Hello again,

Let say I have following user defined function:

fn <- function(x, y) {
		Vec1 <- letters[1:6]
		Vec2 <- 1:5
		return(list(ifelse(x > 0, Vec1, NA), ifelse(y > 0, Vec2, NA)))
	}

Now I have following calculation:
[[1]]
[1] NA

[[2]]
[1] NA
[[1]]
[1] "a"

[[2]]
[1] NA


Here I can not understand why in the second case, I get only the first
element "a" of the corresponding vector 'Vec1'? I want to get complete
vector(s) as the function return.

Can somebody help me how to achieve that?

Thanks and regards,
Rui Barradas
# 
Hello,

You get only one value because ifelse is vectorized, and the condition 
has length(x > 0) == 1. (You get as many values as there are in the 
condition.) Try instead


fn2 <- function(x, y) {
	Vec1 <- letters[1:6]
	Vec2 <- 1:5
	list(if(x > 0) Vec1 else NA, if(y > 0) Vec2 else NA)
}

fn2(-3, -3)
fn2(3, -3)


Hope this helps,

Rui Barradas

Em 22-03-2013 18:43, Christofer Bogaso escreveu:
Peter Ehlers
#
On 2013-03-22 11:43, Christofer Bogaso wrote:
From help(ifelse):
   "ifelse returns a value with the same shape as test"

i.e. in your case, the same 'shape' as 'x > 0', a single value.
You _could_ make ifelse() work with, e.g., ifelse(rep(x, 6) > 0, ....)
but you probably want if() instead.

Peter Ehlers