Skip to content

ifelse() woes ... can we agree on a ifelse2() ?

2 messages · Suharto Anggono Suharto Anggono, Martin Maechler

Original
Suharto Anggono Suharto Anggono
# 
Related to the length of 'ifelse' result, I want to say that "example of different return modes" in ?ifelse led me to perceive a wrong thing in the past.

     ## example of different return modes:
     yes <- 1:3
     no <- pi^(0:3)
     typeof(ifelse(NA,    yes, no)) # logical
     typeof(ifelse(TRUE,  yes, no)) # integer
     typeof(ifelse(FALSE, yes, no)) # double

As the result of each 'ifelse' call is not printed, I thought that the length of the result is 3. In fact, the length of the result is 1.
I realize just now that the length of 'no' is different from 'yes'. The length of 'yes' is 3, the length of 'no' is 4.



--------------------------------------------


 Subject: Re: ifelse() woes ... can we agree on a ifelse2() ?
 To: R-devel at lists.R-project.org
 Date: Sunday, 27 November, 2016, 8:50 AM
 
In all of the proposed 'ifelse'-like functions so far, including from me (that I labeled as 'ifelse2', following Martin Maechler) and from Martin Maechler, the length of the result equals the length of 'test', like in 'ifelse'. There is no recycling of 'test'.
1 day later
Martin Maechler
# 
"of course"... (;-)

But this indeed proves that the example is too sophisticated and
not helpful/clear enough.
Is this better?

## example of different return modes (and 'test' alone determining length):
yes <- 1:3
no  <- pi^(1:4)
utils::str( ifelse(NA,    yes, no) ) # logical, length 1
utils::str( ifelse(TRUE,  yes, no) ) # integer, length 1
utils::str( ifelse(FALSE, yes, no) ) # double,  length 1