R help - May 2005 - A suggestion to improve ifelse behaviour with vector yes/no arguments

Dear All,

I luckily found the following feature (or problem) when tried to apply
ifelse-function to an ordered data.
> test <- c(TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)
> ifelse(test, 0, 1:4)
[1] 0 0 0 4 1 2 3
>
It roots into the ifelse-syntax:

ans[!test & !nas] <- rep(no, length.out = length(ans))[!test & !nas]

Would it be possible to disable this feature in the next R-version? For instance
change the code to be:

ans[!test & !nas] <- rep(no, length.out = length(ans[!test & !nas]))

which seems to solve the problem.

Best regards,

Jussi M??kinen

Jussi M??kinen
Analyst
State Treasury, Finland
www.statetreasury.fi
mailto:jussi.makinen at valtiokonttori.fi

there is nothing problematic there! According to the help-page of 
ifelse(), in the Details section you get:

"If yes or no are too short, their elements are recycled."
                                                ^^^^^^^^
and this is what you get in your example.


Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm




----- Original Message ----- 
From: "M??kinen Jussi" <Jussi.Makinen at valtiokonttori.fi>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, May 31, 2005 4:15 PM
Subject: [R] A suggestion to improve ifelse behaviour with vector 
yes/noarguments

> Dear All,
>
> I luckily found the following feature (or problem) when tried to 
> apply ifelse-function to an ordered data.
>
>> test <- c(TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)
>> ifelse(test, 0, 1:4)
> [1] 0 0 0 4 1 2 3
>>
>
> It roots into the ifelse-syntax:
>
> ans[!test & !nas] <- rep(no, length.out = length(ans))[!test &
!nas]
>
> Would it be possible to disable this feature in the next R-version? 
> For instance change the code to be:
>
> ans[!test & !nas] <- rep(no, length.out = length(ans[!test &
!nas]))
>
> which seems to solve the problem.
>
> Best regards,
>
> Jussi M??kinen
>
> Jussi M??kinen
> Analyst
> State Treasury, Finland
> www.statetreasury.fi
> mailto:jussi.makinen at valtiokonttori.fi
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
>

M??kinen Jussi wrote:
> Dear All,
> 
> I luckily found the following feature (or problem) when tried to apply
ifelse-function to an ordered data.
> 
> 
>>test <- c(TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)
>>ifelse(test, 0, 1:4)
> 
> [1] 0 0 0 4 1 2 3
> 
> 
> It roots into the ifelse-syntax:
> 
> ans[!test & !nas] <- rep(no, length.out = length(ans))[!test &
!nas]
> 
> Would it be possible to disable this feature in the next R-version? For
instance change the code to be:
> 
> ans[!test & !nas] <- rep(no, length.out = length(ans[!test &
!nas]))
> 
> which seems to solve the problem.
As Dimitris said, this is just recycling.  I think getting rid of 
recycling on vectors with length greater than 1 would have been a good 
decision in S about 15 years ago, but it's too late now.

Duncan Murdoch