[R] Am I misunderstanding the ifelse construction?

[Erich Neuwirth]

The thing to remember is that ifelse is a function,
it returns a value, so usually one does not need assignments within the
function call.

You also could do:
negindices <- dir=="-"
gc_content[negindices] <- -gc_content[negindices]

Eik Vettorazzi wrote:
> d <- ifelse(dir == "-", -gc_content , gc_content)
> works. You need not assign gc_content a new value in each comparison,  
> because then your "result" depends only on the last value of "dir", 
> which happened to be "-", so you got -0.5 for all gc_content.
> 
> hth
> 
-- 
Erich Neuwirth, University of Vienna
Faculty of Computer Science
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