Re: moving coefficient.[ch] and design-matrix.[ch]

[Jason Stover]

On Wed, Jun 11, 2008 at 09:32:50AM +0800, John Darrington wrote:
> I'm worried that src/data is becoming a dumping ground for things
> which don't fit elsewhere.  At the same time, src/math is becoming
> depleted.

I noticed the same thing about src/math, but I think that will change
soon when we start adding more mathematical code to support more
procedures.

> I always envisaged src/data to be about the definition, storage and 
> access of data.  The manipulation of data is, as I see it, a seperate,
> higher level task.

Where should coefficient.[ch] and design-matrix.[ch] go? I don't want
to leave it as is because it's causing a circular dependency between
libpspp_math.a and libpspp_linreg.a.

-Jason

> 
> J'
> 
> On Tue, Jun 10, 2008 at 01:45:30PM -0400, Jason Stover wrote:
>      I want to move coefficient.[ch] and design-matrix.[ch] to
>      src/data. Ben and I thought this might be a good idea after discussing
>      it on IRC, so I thought I would elicit more discussion here.
>      
>      coefficient.[ch] and design-matrix.[ch] don't do any computations.
>      They're purpose to offer some common, data-shuffling functionality to
>      model-fitting procedures in src/math/. Right now the only
>      model-fitting code in src/math is linreg, but we will eventually want
>      code for logistic regression and other models. They all need design
>      matrices and coefficients to match variables to columns to
>      coefficients. That matching goes pretty much the same for each kind of
>      model.
>      
>      So it seems that a model-fitting directory in src/math should depend
>      on coefficient.[ch] and design-matrix.[ch]. coefficient.[ch] and
>      design-matrix.[ch] probably should not have to know about
>      model-fitting: there are many kinds of models, and for each of them, a
>      coefficient means the same thing, and a design matrix means the same
>      thing, independently of what kind of model it is.
>      
>      Furthermore, coefficients and design-matrix code doesn't have any math
>      in it. There is no linear algebra, or descent algorithms, etc. That
>      code just takes a coefficient and returns the variable it matches, or
>      vice versa, or takes a variable and finds its corresponding columns in
>      a design matrix.  So putting this in src/math doesn't seem as
>      appropriate as putting it in a place like src/data.
>      
>      coefficient.c depends on linreg.h, but that could be changed. By 
> contrast,
>      design-matrix.c depends on src/data/category.h, and I don't think I could
>      eliminate this dependency.
>      
>      So how does everyone feel about moving coefficient.[ch] and
>      design-matrix.[ch] to src/data? If it sounds good, I'll post a patch.
>      
>      -Jason
>      
>      
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