Deleting rows and columns in matrix based on values in diagonal in R -

with r: if have square matrix, easiest(as fast) way delete row , column if value on diagonal less five? example

       x1  x2  x3  x4     x1 13  15  12  25     x2 23  4   23  34     x3 21  11  1   11     x4 11  22  23  33 

the code delete row 2 , column 2, , row 3 , column 3. tried doing for(i in 1:nrow(mx)), deleting rows changes total number of rows.

the final matrix like

       x1  x4     x1 13  25     x4 11  33 

use diag function , logical comparison < , [ subset operator this...

idx <- ! diag(m) < 5 m <- m[ idx , idx ] 

e.g.

m #   x1 x2 x3 x4 #x1 13 15 12 25 #x2 23  4 23 34 #x3 21 11  1 11 #x4 11 22 23 33  idx <- ! diag(m) < 5     m <- m[ idx , idx ]  m #   x1 x4 #x1 13 25 #x4 11 33