Remove rows in R matrix where all data is NA [duplicate]

Question

Possible Duplicate:
Removing empty rows of a data file in R

How would I remove rows from a matrix or data frame where all elements in the row are NA?

So to get from this:

     [,1] [,2] [,3] [1,]    1    6   11 [2,]   NA   NA   NA [3,]    3    8   13 [4,]    4   NA   NA [5,]    5   10   NA 

to this:

     [,1] [,2] [,3] [1,]    1    6   11 [2,]    3    8   13 [3,]    4   NA   NA [4,]    5   10   NA 

Because the problem with na.omit is that it removes rows with any NAs and so would give me this:

     [,1] [,2] [,3] [1,]    1    6   11 [2,]    3    8   13 

The best I have been able to do so far is use the apply() function:

> x[apply(x, 1, function(y) !all(is.na(y))),]      [,1] [,2] [,3] [1,]    1    6   11 [2,]    3    8   13 [3,]    4   NA   NA [4,]    5   10   NA 

but this seems quite convoluted (is there something simpler that I am missing?)....

Thanks.

Answer 1

Solutions using rowSums() generally outperform apply() ones:

m <- structure(c( 1,  NA,  3,  4,  5,                    6,  NA,  8, NA, 10,                   11,  NA, 13, NA, NA),                 .Dim = c(5L, 3L))  m[rowSums(is.na(m)) != ncol(m), ]       [,1] [,2] [,3] [1,]    1    6   11 [2,]    3    8   13 [3,]    4   NA   NA [4,]    5   10   NA 

Answer 2

Sweep a test for all(is.na()) across rows, and remove where true. Something like this (untested as you provided no code to generate your data -- dput() is your friend):

 R> ind <- apply(X, 1, function(x) all(is.na(x)))  R> X <- X[ !ind, ]