Question

I have the matrix

m <- matrix(c(1, 0, 3, 4, 0, 6), 3)

I need to filter out rows where both columns have a value of 0 in effect returning the matrix:

m <- matrix(c(1, 3, 4, 6), 3)

I have tried

m[m[, 1] > 0 & m[, 2] > 0]

but this returns a vector instead of a matrix stripped of rows with only 0. This should be simple but I am stuck.

Thanks,
-Elizabeth

Answer 1

In case you had many columns

m
     [,1] [,2]
[1,]    1    4
[2,]    0    0
[3,]    3    6
m^2
     [,1] [,2]
[1,]    1   16
[2,]    0    0
[3,]    9   36
rowSums(m^2)
[1] 17  0 45
m[rowSums(m^2)>0,]
     [,1] [,2]
[1,]    1    4
[2,]    3    6