Export residuals from curve fitting

Question

Mohammed Hammad 2019-7-7

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评论： Mohammed Hammad 2019-7-7

Hi,

I am using the curve fitting toolbox on MATLAB_R2019a to create a (linear least square fit) by creating a (Polynomial fit with 1 degree).

I would like to export the residuals values to an array. I know I can acheive that manually from Fit >> Save to work space >> output.

But I have a loop around 1000 file so I would like to export residuals individually for each fit.

Any help is apprciated.

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Answer 1

Matt J 2019-7-7

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编辑：Matt J 2019-7-7

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Instead of using cftool, use the fit() command,

[fitobject,gof,output] = fit(x,y,'poly1','Weights', w);
residuals=output.residuals;

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Mohammed Hammad 2019-7-7

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Thanks a lot, I achieved what I want by editing my curvefit code after generating it from the toolbox as you mentioned

[fitobject,gof,output] = fit( xData, yData, ft, opts );

then I got the residuals from:

residuals=output.residuals;

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Answer 2

Matt J 2019-7-7

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编辑：Matt J 2019-7-7

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For a simple 1 degree polynomial, why not just use polyfit?

p=polyfit(x,y,1);
residuals=polyval(p,x)-y;

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Mohammed Hammad 2019-7-7

cool, but I have weights, how can I insert them in the polyfit function. I used to do that using the curve fitting toolbox but here, I don't know how to do it

Matt J 2019-7-7

编辑：Matt J 2019-7-7

Unfortunately, you cannot do weighted fitting with polyfit, so I would recommend fit() as I mentioned in my other answer.

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