Calculate mean across rows with NA values in R

Question

I have a really simple R question but I can\'t seem to find an adequate solution. Let\'s say we have the following data frame:

groupid<-rep(1:5, each=3)
n         


        

Answer 1

testscores$testMean <- rowMeans(testscores[,3:4], na.rm=TRUE)
> testscores
   groupid    names test1 test2 testMean
1        1     Bill    90    80     85.0
2        1      Jim    70    NA     70.0
3        1    Sarah    90    92     91.0
4        2     Mike    NA    80     80.0
5        2 Jennifer   100    65     82.5
6        2     Bill    90    80     85.0
7        3      Jim    70    NA     70.0
8        3    Sarah    90    92     91.0
9        3     Mike    NA    80     80.0
10       4 Jennifer   100    65     82.5
11       4     Bill    90    80     85.0
12       4      Jim    70    NA     70.0
13       5    Sarah    90    92     91.0
14       5     Mike    NA    80     80.0
15       5 Jennifer   100    65     82.5