If I type
ifelse(TRUE, rep(1,10), 0)
I get 1 instead of 1 1 1 1 1 1 1 1 1 1.
Why? Is this a bug? How can I get the vector of ones?
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Another funny and for some scenarios a handy solution: `x <- T; rep(+x, 9*x+1)` where you either `rep(1, 10)` on `T` or `rep(0, 1)` on `F` – Merijn van Tilborg Feb 03 '22 at 14:53
2 Answers
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Because ifelse is vectorized, it:
returns a value with the same shape as test
Since your test is just a single element vector, your return is just the first element of rep(1, 10).
What you want is if, which expects a single boolean, and then runs the following code, whatever it might be. If you want to return your else statement, then we explicitly include else as below.
if (TRUE) rep(1,10) else 0
#> [1] 1 1 1 1 1 1 1 1 1 1
caldwellst
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You should know that ifelse is vectorized. That means, your output dimensions aligns with the condition. In your code, since condition TRUE is a single value, your output should also be a single value. That's why you get 1 instead of 1 1 1 1 1 1 1 1 1 1.
You can try
> ifelse(rep(TRUE,10), 1, 0)
[1] 1 1 1 1 1 1 1 1 1 1
or
> unlist(ifelse(TRUE, list(rep(1, 10)), 0))
[1] 1 1 1 1 1 1 1 1 1 1
ThomasIsCoding
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But this is not the same functionality. I need a vector from comparing a single value. – quesadagranja Feb 03 '22 at 13:52
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This is not answering the question. OP asks for the "why" of this behavior. – Jaap Feb 03 '22 at 13:52
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