I think, here is the solution. If NA is included in read.table list the row
becomes a factor:
$ Q21: Factor w/ 3 levels " 1"," 2"," NA": 1 2 3 2 2. This will not work
with rowSums.
If I put the missing value as a blank, then it is still read as NA but the
whole row is considered as an integer and OK for rowSums etc.
A missing value in col Q00 will be interpreted as a row with one less value
at the end, I think.
Ian
+ yy <- read.table( header = T, sep=",", text =
+ "Q00, Q20, Q21, Q22, Q23, Q24
+ 0, 0, 1, 2, 3, 4
+ 0, 1, 2, 3, 4, 5
+ 0, 0, NA, 3, 4, 5
+ 0, 1, 2, 3, 4, 5
+ 0, 1, 2, 3, 4, 5")
+ yy
Q00 Q20 Q21 Q22 Q23 Q24
1 0 0 1 2 3 4
2 0 1 2 3 4 5
3 0 0 NA 3 4 5
4 0 1 2 3 4 5
5 0 1 2 3 4 5
+ str(yy)
'data.frame': 5 obs. of 6 variables:
$ Q00: int 0 0 0 0 0
$ Q20: int 0 1 0 1 1
$ Q21: Factor w/ 3 levels " 1"," 2"," NA": 1 2 3 2 2
$ Q22: int 2 3 3 3 3
$ Q23: int 3 4 4 4 4
$ Q24: int 4 5 5 5 5
+ yy <- read.table( header = T, sep=",", text =
+ "Q00, Q20, Q21, Q22, Q23, Q24
+ 0, 0, 1, 2, 3, 4
+ 0, 0, , 3, 4, 5
+ 0, 1, 2, 3, 4, 5")
+ yy
Q00 Q20 Q21 Q22 Q23 Q24
1 0 0 1 2 3 4
2 0 0 NA 3 4 5
3 0 1 2 3 4 5
+ str(yy)
'data.frame': 3 obs. of 6 variables:
$ Q00: int 0 0 0
$ Q20: int 0 0 1
$ Q21: int 1 NA 2
$ Q22: int 2 3 3
$ Q23: int 3 4 4
$ Q24: int 4 5 5
+ x <- transform( yy, ############
Example 6
+ mySum = rowSums(yy[ ,c("Q00","Q20","Q21","Q23")], na.rm=T),
+ myCount =
as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24)),
+ myMean = rowMeans(yy[ ,c("Q00","Q20","Q21","Q23")], na.rm=T)
+ )
+ x
Q00 Q20 Q21 Q22 Q23 Q24 mySum myCount myMean
1 0 0 1 2 3 4 4 3 1.000000
2 0 0 NA 3 4 5 4 2 1.333333
3 0 1 2 3 4 5 7 3 1.750000
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