On Apr 18, 2010, at 12:16 AM, steven mosher wrote:
Is there a simple way to calculate the maximum for a row or column
of a
matrix when there are NA,s present.
# given a matrix that has any number of NA per row
m<-matrix(c(seq(1,9)),nrow=3)
m
[,1] [,2] [,3]
[1,] 1 4 7
[2,] 2 5 8
[3,] 3 6 9
m[3,1]=NA
m[1,]=NA
m
[,1] [,2] [,3]
[1,] NA NA NA
[2,] 2 5 8
[3,] NA 6 9
# applying max to rows doesnt work as max returns
# NA if any of the elements is NA.
row_max<-apply(m,1,max)
row_max
[1] NA 8 NA
# my desired result given m would be:
# NA, 8, 9
Not exactly your desired result, but surely you could fix that:
> row_max<-apply(m,1,max, na.rm=TRUE)
Warning message:
In FUN(newX[, i], ...) : no non-missing arguments to max; returning -Inf
> row_max
[1] -Inf 8 9
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