Re: Polynomial regression - Warning

[Prof J C Nash <nashjc ncf ca>]

Use of the condition number is sensible. If one can detect polynomial 
regression, however, there are alternatives that may improve the 
condition, and it would be nice to tell folk. That's not necessarily 
Gnumeric's job, of course. And there may be more important "bad habits" 
that should be dealt with first. My experience is that users of 
polynomial regression don't want to know they are doing something silly, 
and are wilfully blind to the issues.

There's of course the annoying problem that condition numbers are not 
easy to estimate .... Another story. I'll hopefully be able to provide 
some input and reasonable (i.e., plug out, plug in) fixes after a few 
more months of wading through other projects.

JN

Morten Welinder wrote:
> Unfortunately we cannot really know if the user's use of the tool is sane.
> Yes, a chain saw can be dangerous but it is fundamentally a good tool
> when used right.
>
> What we can do -- at least for the GUI regression tool -- is to check the
> condition number of the relevant matrix.  We do that already and warn
> when the result starts to lose significance.  And err when it is completely
> gone.
>
> Morten
>