Matlab曲线拟合工具cftool生成代码函数没有给出相同的拟合 [英] Matlab curve fitting tool, cftool, generate code function does not give the same fit

问题描述

我正在使用Matlab的曲线拟合工具cftool来拟合我拥有的一组点.我面临的问题是，生成代码函数不会像cftool中产生的那样适合我.

I am using Matlab's curve fitting tool, cftool, to fit a set of points which I have. The problem I am facing is that the generate code function will not give me the same fit as produced in the cftool.

这不是我想要的，因为我希望能够从残差图中检索数据.我也可以只复制cftool中的函数并手动执行.但是我不明白为什么生成的代码不仅会给我同样的曲线拟合.

This is not what I want because I want to be able to retrieve the data from the residual plot. I could also just copy the function from cftool and do it manually. But I do not understand why the generated code will not just give me the same curve fit.

cftool会话文件: http://dl.dropbox.com/u/20782274/test.sfit

从Matlab生成的代码:

The generated code from Matlab:

function [fitresult, gof] = createFit1(Velocity, kWhPerkm)
%CREATEFIT1(VELOCITY,KWHPERKM)
%  Create a fit.
%
%  Data for 'untitled fit 3' fit:
%      X Input : Velocity
%      Y Output: kWhPerkm
%  Output:
%      fitresult : a fit object representing the fit.
%      gof : structure with goodness-of fit info.
%
%  See also FIT, CFIT, SFIT.

%  Auto-generated by MATLAB on 02-Dec-2012 16:36:19


%% Fit: 'untitled fit 3'.
[xData, yData] = prepareCurveData( Velocity, kWhPerkm );

% Set up fittype and options.
ft = fittype( 'a/(0.008*x) + c*x^2 + d*90', 'independent', 'x', 'dependent', 'y' );
opts = fitoptions( ft );
opts.DiffMaxChange = 0.01;
opts.Display = 'Off';
opts.Lower = [-Inf -Inf -Inf];
opts.MaxFunEvals = 1000;
opts.MaxIter = 1000;
opts.StartPoint = [0 0 0];
opts.Upper = [Inf Inf Inf];

% Fit model to data.
[fitresult, gof] = fit( xData, yData, ft, opts );

% Create a figure for the plots.
figure( 'Name', 'untitled fit 3' );

% Plot fit with data.
subplot( 2, 1, 1 );
plot( fitresult, xData, yData, 'predobs' );
% Label axes
xlabel( 'Velocity' );
ylabel( 'kWhPerkm' );
grid on

% Plot residuals.
subplot( 2, 1, 2 );
plot( fitresult, xData, yData, 'residuals' );
% Label axes
xlabel( 'Velocity' );
ylabel( 'kWhPerkm' );
grid on

我用生成的代码得到的曲线: http://i.stack.imgur.com/65d1P.jpg

The curve I get with the generated code: http://i.stack.imgur.com/65d1P.jpg

我需要的曲线: http://i.stack.imgur.com/p3Egp.jpg

那么有人知道出了什么问题吗?

So does anyone know what goes wrong?

-编辑- 以及Velocity和WhPerkm数据文件: http://dl.dropbox.com/u/20782274/data.mat

-edit- And the Velocity and WhPerkm data file: http://dl.dropbox.com/u/20782274/data.mat

推荐答案

RE:我希望能够从残差图中检索数据

一种方法是:

1. 从适合"菜单中选择保存到工作区..."
2. 确保选中将拟合输出保存到名为MATLAB的结构".
3. 请注意变量的名称.默认情况下，它是output.
4. 单击确定"将数据发送到MATLAB工作区.

1. Select "Save to Workspace..." from the Fit menu
2. Ensure that "Save fit output to MATLAB struct named" is checked.
3. Note the name of variable. By default, it is output.
4. Click "OK" to send data to the MATLAB workspace.

在MATLAB工作区中，残差将位于output.residuals中.对于您的示例，您可以通过例如

In the MATLAB workspace, the residuals will be in output.residuals. For your example, you can plot the residuals via, e.g.,

>> plot( Velocity, output.residuals, '.' )

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