A note in the docs seems like a reasonable solution, although I'm not sure I agree that it's a completely transparent design decision. I've always seen the real Schur form presented as an (important) computational trick to avoid complex arithmetic, while the complex form is the mental model. I have a feeling that many users may have never seen the real form before (as a dumb little metric, neither Wikipedia nor Mathworld seem to mention it). To bikeshed for a minute, calling an explicit conversion seems a little bolted on for getting a complex Schur decomposition from a real matrix, which seems like a common use case (at least for the MATLAB-style homework questions like the one I was working on a few hours ago...). Just my two cents.
On Thursday, April 17, 2014 1:15:10 AM UTC-4, Andreas Noack Jensen wrote: > > I prefer the present solution where we use dispatch instead of keywords. I > think it is transparent what is happening: real matrix -> real schur form, > complex matrix -> complex schur form. However, we could add a line in the > documentation explaining it. If you are okay with that idea, please open a > pr. > > > 2014-04-17 6:58 GMT+02:00 Joey Huchette <joehu...@gmail.com <javascript:>> > : > >> Ahh simple enough, thanks. It might be nice to have a keyword argument >> that just dispatches on this---it's not completely obvious that's the right >> thing to do unless you dig around lapack.jl (or get a hint). I can PR. >> >> >> On Thursday, April 17, 2014 12:18:00 AM UTC-4, Andreas Noack Jensen wrote: >> >>> The trick is to convert your matrix to complex before the calculation. >>> >>> schurfact(complex(A))[:T] >>> >>> gives the triangular part. >>> >>> >>> 2014-04-17 1:18 GMT+02:00 Joey Huchette <joehu...@gmail.com>: >>> >>> Is there an implementation in Base (or elsewhere) of a Schur >>>> decomposition that returns a complex matrix matrix T that is triangular? >>>> For reference, MATLAB has a optional switch between the two forms. I >>>> didn't >>>> do enough digging to see if this option is exposed by Lapack, so maybe the >>>> conversion could be done at the Julia level? Apologies if I overlooked it >>>> in the docs/source. >>>> >>> >>> >>> >>> -- >>> Med venlig hilsen >>> >>> Andreas Noack Jensen >>> >> > > > -- > Med venlig hilsen > > Andreas Noack Jensen >
