Why does sample() not work for a single number?

Question

sample(x,n) The parameters are the vector, and how many times you wish to sample

sample(c(5,9),1) returns either 5 or 9

however,

sample(5,1) returns 1,2,3,4, or 5?

I've read the help section:

If x has length 1, is numeric (in the sense of is.numeric) and x >= 1, sampling via sample takes place from 1:x. Note that this convenience feature may lead to undesired behaviour when x is of varying length in calls such as sample(x). See the examples.

But is there a way to make it not do this? Or do I just need to include an if statement to avoid this.

you can use `sample(list(5), 1)` although that will give you a list answer. You might need to go to `sample(list(5), 1)[[1]]` — G5W, Jun 11 '19 at 18:37
Probably duplicate: https://stackoverflow.com/q/13990125/324364 — joran, Jun 11 '19 at 18:46

score 3 · Accepted Answer · answered Jun 11 '19 at 18:35

3

Or do I just need to include an if statement to avoid this.

Yeah, unfortunately. Something like this:

result = if(length(x) == 1) {x} else {sample(x, ...)}

answered Jun 11 '19 at 18:35

Gregor Thomas

136,190
20
167
294

score 2 · Answer 2 · answered Jun 11 '19 at 18:46

2

Here's an alternative approach: you simply subset a random value from your vector like this -

set.seed(4)

x <- c(5,9)
x[sample(length(x), 1)]
[1] 9

x <- 5
x[sample(length(x), 1)]
[1] 5

answered Jun 11 '19 at 18:46

Shree

10,835
1
14
36

Thank you. Very clean solution. – sahimat Jun 11 '19 at 19:46

Why does sample() not work for a single number?

2 Answers2