Curve fitting(toolbox) 3d plot is different when using surf

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Christian York 2022-2-27

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https://ww2.mathworks.cn/matlabcentral/answers/1659720-curve-fitting-toolbox-3d-plot-is-different-when-using-surf

评论： Christian York 2022-2-28

采纳的回答： Matt J

在 MATLAB Online 中打开

I use the curve fitting toolbox and is was what I get:

However, when I try to use 'surf' to plot the 3d plot above it turns out:

[Xtest1, Xtest2] = meshgrid(xtest1, xtest2);
p00 =     -0.4888 ;
p10 =     0.04507 ;
p01 =      0.1304 ;
p20 =    0.005239 ;
p11 =    -0.01134 ;
p02 =   -0.009979 ;
p30 =   0.0005176 ;
p21 =   0.0002514 ;
p12 =   0.0005639 ;
p03 =   0.0002402 ;
z = p00 + p10.*Xtest1 + p01.*Xtest2 + p20.*Xtest1.^2 + p11.*Xtest1.*Xtest2 + p02.*Xtest1.^2 + p30.*Xtest1.^3 + p21.*Xtest1.^2.*Xtest2 + p12.*Xtest1.*Xtest2.^2 + p03.*Xtest2.^3;
surf(Xtest1,Xtest2,z)

The plot using 'surf' is not as same as the plot from curve fitting toolbox at all. Apparently the maximum in curve fitting toolbox and surf plot are different. The data xtest1 and xtest2 are same for both curve fitting toolbox and meshgrid, I wonder what is wrong with the code above?

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采纳的回答

Matt J 2022-2-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1659720-curve-fitting-toolbox-3d-plot-is-different-when-using-surf#answer_905885

编辑：Matt J 2022-2-27

It looks like you have transcribed the fitted coefficients manually from the display, and only to 4 decimal places. (It also looks like you might have interchanged xtest1 with xtest2.)

The more reliable thing to do would be to save the fit tot the Matlab workspace, and then use the fit object to Evaluate the Surface Fit.