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From: "Bruno Luong" <b.luong@fogale.findmycountry>
Newsgroups: comp.soft-sys.matlab
Subject: Re: determining the equation of a 3-D surface
Date: Fri, 21 Nov 2008 19:53:02 +0000 (UTC)
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"loic paccard" <loic.paccard@ecam.fr> wrote in message <gg7322$p7o$1@fred.mathworks.com>...

> Maybe I am wrong, in this case tell me how to use interp2 in order to get this analytical equation z= f(x,y).

I don't think minimizer require an analytic expression. All it needs is you will be able to evaluate a function - preferable continuously derivable - at any point.

And that is exactly interp2 with spline function can give you.

Otherwise you have to give up the fact that the model (could be an analytic expression) interpolate the data, but only *approximate* your data. In this case you might call a fitting with multi-variate polynomial, or spline functions.

Bruno