[R] if documentation
m@ech|er @end|ng |rom @t@t@m@th@ethz@ch
Wed Dec 7 12:16:03 CET 2022
>>>>> PIKAL Petr
>>>>> on Wed, 7 Dec 2022 07:04:38 +0000 writes:
> Hallo all Not sure if it is appropriate place but as I am
> not involved in r-devel list I post here.
> Documentation for Control (if, for, while, .) is missing
> "if else" command. Although it can be find online
> elsewhere I believe that adding it either as an example or
> as a third entry and paragraph about nested if's could be
> if(cond) cons.expr else if (cond) alt.expr else alt2.expr
> Nested if expressions are better realized with "else if"
> instead of sequence of plain "else" control statements
> especially when using several of them.
I agree. However there is no "else if" special.
As everything that *happens* in R is a function call (John Chambers),
indeed, `if` is a function too, with an unusual syntax which may
If you look more closely, `if` is a function with 3 arguments,
where the last (3rd) is optional and has a default of NULL :
Some code towards proving the above :
(t1 <- if(TRUE) 1:3 ) # is identical to if(TRUE) 1:3 else NULL
f1 <- if(FALSE) 1:3 # is identical to
f2 <- if(FALSE) 1:3 else NULL
f3 <- if(FALSE) 1:3 else 111
`if`(TRUE, 1:3, NULL)
`if`(FALSE, 1:3) # returns invisibly
`if`(FALSE, 1:3, NULL)
`if`(FALSE, 1:3, 111)
So, 'if(.) else' or 'if(...) else if(..) ..'
all just versions of calling the `if` function sometimes, in a
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