Handling NA values
Thanks Marc for your reply. However this leads to my problem of handling rowSums() function (hence colSums()). Let take following matrix:
Mat <- matrix(c(1, 1, NA, -1, 1, NA, NA, 1, NA), nc = 3) Mat
[,1] [,2] [,3] [1,] 1 -1 NA [2,] 1 1 1 [3,] NA NA NA
rowSums(Mat, na.rm = TRUE)
[1] 0 3 0 I want to have some way to distinguish the 1st '0' and the 3rd '0'. I want to see NA directly for the 3rd. Any possibility how to do that through the rowSum() function? Thanks and regards,
On Sat, Feb 16, 2013 at 11:52 PM, Marc Schwartz <marc_schwartz at me.com> wrote:
On Feb 16, 2013, at 11:55 AM, Christofer Bogaso <bogaso.christofer at gmail.com> wrote:
Hello again, I have a question on who sum() handle the NA values.
sum(c(NA, 1), na.rm = TRUE)
[1] 1 I understand this. However could not agree with following:
sum(c(NA, NA), na.rm = TRUE)
[1] 0 Where this '0' is coming from? Should not it be NA itself? Thanks and regards,
The result of: sum(c(NA, NA), na.rm = TRUE) is to sum an empty set, hence the 0.
na.omit(c(NA, NA))
logical(0) attr(,"na.action") [1] 1 2 attr(,"class") [1] "omit"
sum(logical(0))
[1] 0 If you retained the NA's, then the result is undefined:
sum(c(NA, NA))
[1] NA See: http://rwiki.sciviews.org/doku.php?id=tips:surprises:emptysetfuncs for more information. Regards, Marc Schwartz