Re: Polynomial regression - Warning

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.


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


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