MAINT: GLM

Addresses (or partially addresses) several issues with GLM:

* Allow use of maxiter==0 to evaluate the likelihood at a given point (closes #1728).  Previously maxiter==0 was doing one iteration (should be zero iterations).  Added a test for this use case.

* Rename eta -> lin_pred and Y -> endog in many places.  Partially closes #1685, but I didn't do anything with mu (naming issues with links, e.g. fitted and predict still stand).

* Rename confusing keyword argument fittedvalues in the negative binomial log likelihood to  lin_pred (which is what it really is).

* Avoid making unneeded copy of offset (second part of #1720)
I can revert the y->endog changes in family.  Just give me some guidance on
how to proceed with renamings.


On Mon, Jun 9, 2014 at 3:05 AM, Josef Perktold <notifications@github.com>
wrote:

> In statsmodels/genmod/families/family.py:
>
> >              return -2 * np.sum(one * np.log(mu+1e-200) + (1-one) * np.log(1-mu+1e-200))
> >
> >          else:
> > -            return 2*np.sum(self.n*(Y*np.log(Y/mu+1e-200)+(1-Y)*np.log((1-Y)/(1-mu)+1e-200)))
> > +            return 2*np.sum(self.n*(endog*np.log(endog/mu+1e-200)+(1-endog)*np.log((1-endog)/(1-mu)+1e-200)))
>
> general taste issue:
> In pure math, I find using y and x locally improves readability, y =
> endog # alias
> here missing whitespace makes it difficult to read
>
> —
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> <https://github.com/statsmodels/statsmodels/pull/1734/files#r13525584>.
>