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

Martin Maechler maechler at lynne.stat.math.ethz.ch
Mon Jan 26 13:45:45 CET 2015

```>>>>> Jim Lemon <drjimlemon at gmail.com>
>>>>>     on Mon, 26 Jan 2015 11:21:03 +1100 writes:

> 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.

"Do NOT use ifelse()"

-- include the quotes in your search --

or directly at
http://stat.ethz.ch/pipermail/r-help/2014-December/424367.html

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
>> 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