[R] Advice on recoding a variable depending on another which contains NAs

[Jeff Newmiller]

No, you use it once and it does the whole vector at once.
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Sent from my phone. Please excuse my brevity.

Anthony Staines <anthony.staines at dcu.ie> wrote:

>Ah,
>so that's how ifelse gets used...
>
>Presumably if I had more than 2 non-missing values in the 
>control variable, I could use it several times.
>
>Thank you very much, for a really useful answer, and thanks 
>for getting back so quickly!
>
>All the best,
>Anthony Staines
>
>On 11/19/11 23:55, David Winsemius wrote:
>>
>> On Nov 19, 2011, at 6:31 PM, Anthony Staines wrote:
>>
>>
>> This would seem to be an obvious task for ifelse()
>>
>> SCQScore <- NA
>> d$SCQScore <- ifelse( SCQ1 == 1, d$SCQScore1, d$SCOScore2)
>>
>> (And don't use 99 for missing. Use NA. It will protect you
>> better than "99".)
>>
>>
>> I suppose you could enforce the two level testing with:
>>
>> d$SCQScore <- ifelse( SCQ1 == 1, d$SCQScore1,
>> ifelse(SCQ1 ==2, d$SCOScore2, NA))
>>
>>>
>>> d$SCQScore <- 99
>>> ##Distinct value for any other values I've missed
>>>
>>> d$SCQScore[SCQ1 == 1] <- d$SCQScore1[SCQ1 == 1]
>>> ## Talks using phrases/sentences, so sum S2CQ:SCQ40
>>>
>>> d$SCQScore[SCQ1 == 2] <- d$SCQScore2[SCQ1 == 2]
>>> ## Can't do this, so sum SCQ8:SCQ40
>>>
>>> d$SCQScore[is.na(d$SCQ1)] <- d$SCQScore1 [is.na(d$SCQ1)]
>>> ## SCQ1 is missing
>>>
>>> This fails on line 2
>>> (d$SCQScore[SCQ1 == 1] <- d$SCQScore1[SCQ1 == 1])
>>> with the error message
>>> "NAs are not allowed in subscripted assignments",
>>> presumably because SCQ1 does indeed contain missing values.
>>>
>>> This can be fixed, got around, or otherwise bypassed, by
>>> creating a new variable SCQ1, with no missing values, as
>>> shown :-
>>>
>>> SCQ1 <- d$SCQ1
>>> SCQ1[is.na(SCQ1)] <- 3
>>>
>>> d$SCQScore[SCQ1 == 1] <- d$SCQScore1[SCQ1 == 1]
>>> ## Talks using phrases/sentences so sum S2CQ:SCQ40
>>> d$SCQScore[SCQ1 == 2] <- d$SCQScore2[SCQ1 == 2]
>>> ## Can't do this, so sum SCQ8:SCQ40
>>> d$SCQScore[SCQ1 == 3] <- d$SCQScore1[SCQ1 == 3]
>>> ## We don't know if he/she can talk, so guess - sum S2:S40
>>>
>>> This type of thing is a common problem in my little world.
>>> Is there a better/less klutzy/smarter way of solving it
>>> than creating a new variable each time? Please bear in
>>> mind that it is critical, for later analysis, to keep the
>>> missing values in SCQ1.
>>>
>>> Best wishes,
>>> Anthony Staines
>>> --
>>> Anthony Staines, Professor of Health Systems,
>>> School of Nursing and Human Sciences, DCU, Dublin 9,Ireland.
>>> Tel:- +353 1 700 7807. Mobile:- +353 86 606 9713
>>> http://astaines.eu/
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained,
>>> reproducible code.
>>
>> David Winsemius, MD
>> West Hartford, CT
>>
>
>-- 
>Anthony Staines, Professor of Health Systems,
>School of Nursing and Human Sciences, DCU, Dublin 9,Ireland.
>Tel:- +353 1 700 7807. Mobile:- +353 86 606 9713
>http://astaines.eu/
>______________________________________________
>R-help at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.