Dear Friends.
I found a puzzling phenomenon in R when you use 'if' within a function:

# defining a function aaa
aaa=function(a)
{if (a==1) {aaa=1};
 if (a!=1) {aaa=2}
 }

# using the function:
> b=20
> bbb=aaa(b)
> bbb
[1] 2
> typeof(bbb)
[1] "double"
>
>
> c=1
> ccc=aaa(c)
> ccc
NULL
> typeof(ccc)
[1] "NULL"

It seems that only the last 'if' phrase works. Is it an instrinsic weakness
of R? Is there a way to get around it? ( I use 'elseif' to get around this
when there are only two cases to choose from, but what if there are more
than two cases to choose from?)

Best
Yuchen

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