Poly11: "Warning: Equation is badly conditioned. Remove repeated data points or try centering and scaling."

47 次查看（过去 30 天）
Zachary Ferrie
Zachary Ferrie 2019-2-21
评论： Zachary Ferrie 2019-2-25
Hi All,
I have the below code running on MATLAB which produces the warning message (also shown below). I am trying to figure out what why the warning message is appering.
My guess is that since the values i use for my fit are similar I get the message but I want to be sure that nothing is going wrong.
I am trying to fully understand things.
Thanks
%INPUT
xy = [3154384.896 1719923.63; 3155030.31 1719242.07; 3155498.37 1719245.31];
z =
1.0e+03 *
5.121466000000001
5.126727000000000
5.126100000000000
R = fit(xy, z, 'poly11') % 'polly11' fit = fit linear polynomial surface. For more info visit: https://www.mathworks.com/help/curvefit/fit.html
coeffs = coeffvalues(R)
Slopex = coeffs(2) %extract slope x
Slopey = coeffs(3) %extract slope y
%OUTPUT
Warning: Equation is badly conditioned. Remove repeated data points or try centering and scaling.
> In curvefit.attention.Warning/throw (line 30)
In fit>iLinearFit (line 672)
In fit>iFit (line 383)
In fit (line 108)
Linear model Poly11:
R(x,y) = p00 + p10*x + p01*y
Coefficients:
p00 = 2.451e+04
p10 = -0.001278
p01 = -0.008929
coeffs =
1.0e+04 *
2.450931465568791 -0.000000127776324 -0.000000892905436

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2019-2-21
The problem is not in the z: the problem is in the y values being very similar.
Your fit can be rewritten as
p = [ones(3,1), xy] \ z
and for that the sensitivity can be estimated by cond([ones(3,1),xy]) which comes out about 1E11 .

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Get Started with Curve Fitting Toolbox 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by