[R] conditional rowsums in sapply

[David Winsemius]

On May 16, 2011, at 10:25 AM, Assu wrote:

> Hi all
>
> I have a data frame with duplicate columns and i want to remove  
> duplicates
> by adding rows in each group of duplicates, but have lots of NA's.
> Data:
> dfrm <- data.frame(a = 1:4, b= 1:4, cc= 1:4, dd=1:10, ee=1:4)
> names(dfrm) <- c("a", "a", "b", "b", "b")
> dfrm[3,2:3]<-NA
> dfrm
>    a  a  b  b  b
> 1   1  1  1  1  1
> 2   2  2  2  2  2
> 3  NA NA NA  3  3
> 4   4  4  4  4  4
> I did: sapply(unique(names(dfrm)),function(x){
> rowSums(dfrm[ ,grep(x, names(dfrm)),drop=FALSE])})
> which works. However, I want rowSums conditional:
> 1) if there is at least one value non NA in a row of each group of
> duplicates, apply rowSums to get the value independently of the  
> existence of
> other NA's in the group row.
> 2) if all values in a row of duplicates are NA, I get NA
> In my data dfrm I would get
>
>     a   b
> 1    2   3
> 2    4   6
> 3   NA  6
> 4    8  12
> Can't use na.rm=TRUE or FALSE.
> I tried: sapply(unique(names(dfrm)),function(x) ifelse(any(! 
> is.na(dfrm[
> ,grep(x, names(dfrm))])), rowSums(dfrm[ ,grep(x,
> names(dfrm)),drop=FALSE],na.rm=TRUE),NA))
>
> and it doesn't work.
> Can someone please help me?
> Thanks in advance.

You didn't like the answer I posted last night on SO?
sapply(unique(names(dfrm)),
       function(x) apply(dfrm[grep(x, names(dfrm))], 1,
               function(y) if ( all(is.na(y)) ) {NA} else { sum(y,  
na.rm=TRUE) }
        )               )

-- 
David.
>
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-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT