[R] Handling "NA" in summation

Dan D ddalthorp at usgs.gov
Mon Sep 7 01:50:38 CEST 2015

# it's not clear what your question is, but here's a stab in the dark at a

ind<- !is.na(dataframe$A) & !is.na(dataframe$B)
dataframe$A[ind] + dataframe$B[ind] 

- Dan

P.S. I'm sure there are ways to do this using one of R's functions for
automatically removing NA's (na.rm = T), but unless you use them all the
time, their behavior is not always predictable (e.g., sometimes it ignores a
whole row with one NA in it; sometimes it treats NAs as zeros). Explicitly
defining  the indices that you want to exclude may make it easier to avoid
difficult-to-find errors.

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