Re: Matrix column access

>>>>> "Raymond" == Raymond Toy <[email protected]>:
>>>>> "Jan" == Jan Rychter <[email protected]> writes:
 Jan> I started using matlisp very recently and the things that were
 Jan> missing were:

 Jan> -- why wasn't pinv (pseudoinverse) incorporated? I had to put it
 Jan>    in myself, and the patches were posted to the list some months ago...

 Raymond> Mostly because no one wanted it early on, and later because I
 Raymond> was lazy.

Fair enough!

 Raymond> It also doesn't help my motivation when someone (not you!) 
 Raymond> asks for some functionality, and I ask a question about it,
 Raymond> and never hear from him again.

Well, we'll try to be better this time :-)

 Jan> -- not enough efficient data manipulation tools: the macros I
 Jan>    posted for operating on rows and columns are an example. I
 Jan>    really really need those to do anything serious.

 Raymond> What other kind of data manipulation tools are you looking
 Raymond> for?

Basically, something corresponding to my extract-row and extract-column
macros.

An important point in my case is that I'd like to have extra-efficient
versions of those for some operations. Ideally I'd like to be able to do
an (m- (extract-column m i) b) without actually copying the elements of
that column.

 Jan> -- minor stuff, like min/max.
 Raymond> This kind of stuff isn't there mostly because of my laziness,
 Raymond> and because of the lack of requests for such functionality.
 Raymond> Plus, what is min/max supposed to do on a matrix?  Return the
 Raymond> min/max element of the matrix?

I use these mostly on vectors, on matrices I'd like to have a row-major
and a column-major min/max, each returning a vector. Perhaps a min/max
on the entire matrix is useful for people as well, I don't know.

--J.



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