Curve Fitting for an equation
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Hello
I have an equation like a*(x1^2)+ b(x2^2)+c((x1-x2)^2)+d((x12)^2)=1. Here I have variables of x1, x2, x12. x12 is the variable in the first quardrant. I have data of 12 Points passing through x1, x2 and x12.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/196745/image.jpeg)
I tried fitting the data to the above equation with different ways. But it did not turned out good. I tried with custom equation and some other methods. Could someone help me with getting the coefficients to this equation.
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Accepted Answer
Torsten
on 1 Oct 2018
Edited: Torsten
on 1 Oct 2018
function main xdata = [...]; % x coordinates of your 12 point ydata = [...]; % y coordaintes of your 12 points x0 = [1 1 1]; % initial values for a, b and c x = lsqnonlin(@(x)fun(x,xdata,ydata),x0) end
function res = fun(x,xdata,ydata) res = x(1)*xdata.^2+x(2)*ydata.^2+x(3)*(xdata-ydata).^2-1; end
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More Answers (1)
Pratik Bajaria
on 28 Sep 2018
4 Comments
Pratik Bajaria
on 29 Sep 2018
Well all equations can be written in y=f(x). Take any of the variables to be y (let's say x12) and all the other variables can be x. Since you have data points available try to write x12=f(x1,x2) and it must work.
Regards.
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