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Subject: Important Regression Questions
Date: Wed, 4 Nov 2009 17:13:03 +0000 (UTC)
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Hi,

I have a few confusions about Regression!

First, I have seen regression can be applied to either 'linear' or 'non linear' models 

BUT!!!

1 - What is the best criteria to see that the fitted curve or line is the best model e.g. one way could be to compare the values of norm of residuals....is there any other? 

2- when I do regstats (x,y), then it gives me very useful information e.g. value of   R-square etc. but are these values calculated based on a linear model or does it calculate the values fitting the best possible model?

3- why is it so that for nonlinear, one must have some formula in mind to apply. Is not it possible that I simply input my data and matlab itself decides whats the best fit (non linear).

Thanks for ur time.