How to combine 2 variables and ignore NAs

Question

I have some data like these

var1   var2
10     NA
101    NA
NA     86
11     NA
NA     11
NA     61

If one variable is NA then the other one is

Answer 1

rowSums with na.rm = TRUE will do this. (This is your suggested solution really...)

Assuming your data are in a data.frame DF and your comment

If one variable is NA then the other one is not, and vice-versa.

is true.

 DF$var3 <- rowSums(DF[, c('var1','var2')], na.rm = TRUE)