[R] Sum function and missing values --- need to mimic SAS sum function
John Fox
jfox at mcmaster.ca
Mon Jan 26 01:17:53 CET 2015
Dear Allen,
This seems reasonably straightforward to me, suggesting that I might not properly understand what you want to do. How about something like the following?
> mysum <- function(...){
+ x <- c(...)
+ if (all(is.na(x))) NA else sum(x, na.rm=TRUE)
+ }
> mysum(1, 2, 3, NA)
[1] 6
> mysum(1:3)
[1] 6
> mysum(NA, NA, NA)
[1] NA
> mysum(c(NA, NA, NA))
[1] NA
I hope this helps,
John
------------------------------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox/
On Sun, 25 Jan 2015 15:21:52 -0800
"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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