Re: surface fitting question
- To: mathgroup at smc.vnet.net
- Subject: [mg61389] Re: surface fitting question
- From: "Ray Koopman" <koopman at sfu.ca>
- Date: Tue, 18 Oct 2005 02:44:30 -0400 (EDT)
- References: <email@example.com><firstname.lastname@example.org>
- Sender: owner-wri-mathgroup at wolfram.com
Ralph Smith wrote: > [...] The Fit with polynomials is way off at x=0. > All of the z values should be 0 but I'm getting > numbers like 100 or so for the surface along that line. To force z = 0 at x = 0, try fitting something like z = a30 x^3 + a21 x^2 y + a12 x y^2 + a20 x^2 + a11 x y + a10 x which is cubic without the x^0 terms.