Hello, There are 2 interfaces for the QR decomposition, the original interface which uses Level-2 BLAS, and a recently added interface using Level-3 BLAS (_r suffix to function names). In both cases, there is an "unpack" function to extract the Q matrix:
gsl_linalg_QR_unpack gsl_linalg_QR_unpack_r The R matrix is always stored in the upper triangle of the input matrix (A) by the QR_decomp routines. In most applications, you never need to actually construct the full Q matrix itself. If you describe more about what you want to do, or post your source code, we can probably help more. Thanks, Patrick On 1/30/21 1:49 AM, Iaroslav Postovalov wrote: > Hello, > > I'm quite confused with using QR decomposition with GSL. The library > returns data in very unclear data format, and I don't understand how to get > Q and R matrices from it. > > Certain users may have the same problem for other decompositions (since > literally all of them require some effort to extract the resulting > matrices), and I think that the GSL documentation has to provide some > instructions for them. > > All the bests, > Iaroslav
