[R] rowSums()

[Doran, Harold]

Say I have the following data:

testDat <- data.frame(A = c(1,NA,3), B = c(NA, NA, 3))

> testDat
   A  B
1  1 NA
2 NA NA
3  3  3

rowsums() with na.rm=TRUE generates the following, which is not desired:

> rowSums(testDat[, c('A', 'B')], na.rm=T)
[1] 1 0 6

rowsums() with na.rm=F generates the following, which is also not
desired:


> rowSums(testDat[, c('A', 'B')], na.rm=F)
[1] NA NA  6

I see why this occurs, but what I hope to have returned would be:
[1] 1 NA  6

To get what I want I could do the following, but normally my ideas are
bad ideas and there are codified and proper ways to do things. 

rr <- numeric(nrow(testDat))
for(i in 1:nrow(testDat)) rr[i] <- if(all(is.na(testDat[i,]))) NA else
sum(testDat[i,], na.rm=T)

> rr
[1]  1 NA  6

Is there a "proper" way to do this? In my real data, nrow is over
100,000

Thanks,
Harold

> sessionInfo()
R version 2.7.2 (2008-08-25) 
i386-pc-mingw32 

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base


other attached packages:
[1] MiscPsycho_1.2  lattice_0.17-13 statmod_1.3.6  

loaded via a namespace (and not attached):
[1] grid_2.7.2