QR/RQ/QL/LQ factorizations
Currently RQ, QL, and LQ factorizations are not included in Matlab, although these factorizations can also be done by QR function and additional matrix manipulations if matrix is square. Therefore I wrote these mex files, which uses the internal LAPACK routines of Matlab. QR1 is added to complete the set. They can also handle empty matrices. Enforcing positive elements on diagonal R matrix or column pivoting is supported by the QR1 factorization only.