Export residuals from curve fitting

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.

Answer 1

[Matt J]

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

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

residuals=output.residuals;

[Mohammed Hammad]

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; 

Answer 2

[Matt J]

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

p=polyfit(x,y,1);

residuals=polyval(p,x)-y;

[Mohammed Hammad]

Thanks for the prompt answer. Is polyfit(x,y,1) gives the same linear least square fit?

[Matt J]

Yes, if you really are just doing a 1D line fit.

[Mohammed Hammad]

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]

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