Eventually, we should support multiplying with Q in the same way it possible with dense QR. It will require that we introduce a Q type for sparse QR for which we can overload the usual matrix multiplication functions by appropriate calls to qmult. Notice however that qmult is only defined for multiplication with dense matrices. The C API only supports part of the functionality availible in SPQR. You could look into wrapping SuiteSparseQR_C_QR in a method similar to qr (i.e. not qrfact) which will give what you want. A PR would be very welcome.
Finally, you are probably aware, but notice that Q will have a lower sparcity than the original matrix so it is often recommened to avoid constructing it explicitly. On Tuesday, January 12, 2016 at 8:34:48 AM UTC-5, Christopher Rinderspacher wrote: > > Dear All, > > I need direct access to Q and R of a sparse matrix for one of my > algorithms. Currently, it seems the API does not support this, although > internally spqr.jl implements qmult, which I presume I could use if it was > exposed to multiply Q with the identity (in a sparse format) to get Q. > Similarly with R. Are there any plans to expose appropriate APIs? > > Sincerely, > > Christopher >
