How to use lsqcurvefit to find constant values?
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Hi
How to use 'lsqcurvefit' to find the coefficient values 'a' and 'b'.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/147970/image.png)
The blue line(A1) is produced from the experimental data and the green line is based on the 'nlinfit' function. But the error is very high.
Is it possible to use 'lsqcurvefit' and find the constant values?
A1=[......] % experimental data
A2= a*exp(b/X)*Y %function for greenline.
X=[.........] Y=[.........] I know the values of X and Y.
The ultimate aim is to reduce the error and finding the best fitted constant values.
Thanks
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Star Strider
le 16 Mar 2015
Modifié(e) : Star Strider
le 16 Mar 2015
You have to create a single matrix of your ‘X’ and ‘Y’ values:
XY = [X(:) Y(:)];
Then create your objective function ‘A2’ as:
% b(1) = a, b(2) = b
A2 = @(b, XY) b(1) .* exp(b(2)./XY(:,1)) .* XY(:,2);
And give it to lsqcurvefit as:
B0 = randi(10, 2, 1); % Choose Appropriate Initial Parameter Estimates
B = lsqcurvefit(A2, B0, XY, A1);
Where ‘B(1)=a’ and ‘B(2)=b’.
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Star Strider
le 16 Mar 2015
My pleasure.
I get a significantly different plot from the figure you posted. What data did you use to create it?
What figure do you get when you use my code?
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