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

[Martin Maechler]

>>>>> 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

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
    >> 
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    > ______________________________________________
    > 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.