[R] Sum function and missing values --- need to mimic SAS sum function

[Bert Gunter]

Huh??

> ifelse(TRUE, a <- 2L, a <- 3L)
[1] 2
> a
[1] 2

Please clarify.

-- Bert

Bert Gunter
Genentech Nonclinical Biostatistics
(650) 467-7374

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
Clifford Stoll




On Mon, Jan 26, 2015 at 2:22 PM, Hervé Pagès <hpages at fredhutch.org> wrote:
> Hi Martin,
>
> On 01/26/2015 04:45 AM, Martin Maechler wrote:
>>>>>>>
>>>>>>> Jim Lemon <drjimlemon at gmail.com>
>>>>>>>      on Mon, 26 Jan 2015 11:21:03 +1100 writes:
>>
>>
>>      > Hi Allen, How about this:
>>
>>      > sum_w_NA<-function(x) ifelse(all(is.na(x)),NA,sum(x,na.rm=TRUE))
>>
>> Excuse, Jim, but that's yet another  "horrible misuse of  ifelse()"
>>
>> John Fox's reply *did* contain  the "proper" solution
>>
>>       if (all(is.na(x))) NA else sum(x, na.rm=TRUE)
>>
>> The ifelse() function should never be used in such cases.
>> Read more after googling
>>
>>      "Do NOT use ifelse()"
>>
>>      -- include the quotes in your search --
>>
>> or directly at
>>     http://stat.ethz.ch/pipermail/r-help/2014-December/424367.html
>
>
> Interesting. You could have added the following item to your list:
>
>   4. less likely to play strange tricks on you:
>
>      > ifelse(TRUE, a <- 2L, a <- 3L)
>      [1] 2
>      > a
>      [1] 3
>
> Yeah I've seen people using ifelse() that way and being totally
> confused...
>
> Cheers,
> H.
>
>>
>> Yes, this has been on R-help a month ago..
>> Martin
>>
>>      > On Mon, Jan 26, 2015 at 10:21 AM, Allen Bingham
>>      > <aebingham2 at gmail.com> wrote:
>>      >> I understand that in order to get the sum function to
>>      >> ignore missing values I need to supply the argument
>>      >> na.rm=TRUE. However, when summing numeric values in which
>>      >> ALL components are "NA" ... the result is 0.0 ... instead
>>      >> of (what I would get from SAS) of NA (or in the case of
>>      >> SAS ".").
>>      >>
>>      >> Accordingly, I've had to go to 'extreme' measures to get
>>      >> the sum function to result in NA if all arguments are
>>      >> missing (otherwise give me a sum of all non-NA elements).
>>      >>
>>      >> So for example here's a snippet of code that ALMOST does
>>      >> what I want:
>>      >>
>>      >>
>>      >>
>> SumValue<-apply(subset(InputDataFrame,!is.na(Variable.1)|!is.na(Variable.2),
>>      >> select=c(Variable.1,Variable.2)),1,sum,na.rm=TRUE)
>>      >>
>>      >> In reality this does NOT give me records with NA for
>>      >> SumValue ... but it doesn't give me values for any
>>      >> records in which both Variable.1 and Variable.2 are NA
>>      >> --- which is "good enough" for my purposes.
>>      >>
>>      >> I'm guessing with a little more work I could come up with
>>      >> a way to adapt the code above so that I could get it to
>>      >> work like SAS's sum function ...
>>      >>
>>      >> ... but before I go that extra mile I thought I'd ask
>>      >> others if they know of functions in either base R ... or
>>      >> in a package that will better mimic the SAS sum function.
>>      >>
>>      >> Any suggestions?
>>      >>
>>      >> Thanks.  ______________________________________ Allen
>>      >> Bingham aebingham2 at gmail.com
>>      >>
>>      >> ______________________________________________
>>      >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and
>>      >> more, see 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.
>>
>>      > ______________________________________________
>>      > R-help at r-project.org mailing list -- To UNSUBSCRIBE and
>>      > more, see 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.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>>
>
> --
> Hervé Pagès
>
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
> P.O. Box 19024
> Seattle, WA 98109-1024
>
> E-mail: hpages at fredhutch.org
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.