I am trying to find the orthonormal basis of the null space as defined by the matrix A (mxn).
I tried the following steps:
1) Did the QR decomposition on the transpose of A using DGEQRF.
2) Directed the resulting output of A to DORMQR.
I was expecting the last (n-m) columns of C should contain the orthonormal basis of the null space but does not seem so.
Could you pls clarify if these are the right steps?
I have also tried DGESVD and it worked correctly as long as m is 1. When m happened to be greater than 1 but less than n, this method didn't give correct results.
Are there any other methods?