Using matrix decompositions

[Iaroslav Postovalov]

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