Calculate mean across rows with NA values in R

testscores$testMean <- rowMeans(testscores[,3:4], na.rm=TRUE)> testscores   groupid    names test1 test2 testMean1        1     Bill    90    80     85.02        1      Jim    70    NA     70.03        1    Sarah    90    92     91.04        2     Mike    NA    80     80.05        2 Jennifer   100    65     82.56        2     Bill    90    80     85.07        3      Jim    70    NA     70.08        3    Sarah    90    92     91.09        3     Mike    NA    80     80.010       4 Jennifer   100    65     82.511       4     Bill    90    80     85.012       4      Jim    70    NA     70.013       5    Sarah    90    92     91.014       5     Mike    NA    80     80.015       5 Jennifer   100    65     82.5

you can also use this

testscores <- structure(list(groupid = c(1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L, 5L, 5L, 5L), names = structure(c(1L, 3L, 5L, 4L, 2L, 1L, 3L, 5L, 4L, 2L, 1L, 3L, 5L, 4L, 2L), .Label = c("Bill", "Jennifer", "Jim", "Mike", "Sarah"), class = "factor"), test1 = c(90, 70, 90, NA, 100, 90, 70, 90, NA, 100, 90, 70, 90, NA, 100), test2 = c(80, NA, 92, 80, 65, 80, NA, 92, 80, 65, 80, NA, 92, 80, 65)), .Names = c("groupid", "names", "test1", "test2"), row.names = c(NA, -15L), class = "data.frame")testscores$meanTest=rowMeans(testscores[,c("test1", "test2")], na.rm=TRUE)#   groupid    names test1 test2 meanTest#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