Curvefitting a given function with parameters to pass through given points
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I need to curve fit a given data with a function which contains a few parameters. I need to find the values of those parameters. But I need the curve to pass through certain given points too. How do I do this
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Torsten
2018-6-6
0 个投票
Each prescribed point on the curve gives you a relation between the parameters to be estimated. These relations are constraints for the curve fitting process. You can use MATLAB's "fmincon" together with the "nonlcon" function for nonlinear constraints or the Aeq,beq arrays for linear constraints.
Best wishes
Torsten.
3 个评论
AAKILA RAJAN
2018-6-6
Torsten
2018-6-6
Example:
If
p(x)=a*x^2+b*x+c+d*exp(e*x)
is the form of the fitting function and you want to have p(xend) to have a specified value yend, you get the constraint
yend - (a*xend^2+b*xend+c+d*exp(e*xend)) = 0
This constraint has to be implemented in fmincon's "nonlcon" as
ceq(1) = yend - (p(1)*xend^2+p(2)*xend+p(3)+p(4)*exp(p(5)*xend))
And the objective function for the problem is the sum of squared differences between measured and fitted data.
Best wishes
Torsten.
AAKILA RAJAN
2018-6-6
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2018-6-6
2018-6-6
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