fminsearch for complex input for curve fitting

2014 10 23
2 个回答
更新时间：2014 10 29
5 次查看（30 天）

0 个投票

Dear all, I would like to fit experimental data with custom equations. I aim for the best fit of the theoretical curve to the experimental data by minimizing the residuals and use fminsearch to find minimal error.
The attached code works well for the real inputs
[R, fval] = fminsearch(err, 2.11)% finds the minimum of err But it fails for the
[R, fval] = fminsearch(err, 2.0-0.064i)
Help for fminsearch suggests to input split into real, imaginary parts and work to obtain the best fit. I have a little idea of doing this.
Could somebody help me with this problem? Thanks all.

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

VISWANATH
VISWANATH 2014-10-28
I used
% Absolute error err = @ (n1) sum((abs(Rtot_s(n1)).^2 - S).^2 + (abs(Rtot_p(n1)).^2 - P).^2) % Minimum search for the error value x0 = complex(2.1,-0.07) [R, fval, exitflag] = lsqnonlin(@(x)err(x), real(x0),imag(x0) )
O/p R =
2.1084
fval =
28.0003
exitflag =
5.2915

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

Matt J
Matt J 2014-10-23
编辑：Matt J 2014-10-23

0 个投票

Assuming your err function is real-valued,
[R, fval] = fminsearch(@(x) err( complex( x(1),x(2) ) ), [2.0,0.064])

4 个评论
显示 2更早的评论 隐藏 2更早的评论

VISWANATH
VISWANATH 2014-10-27
tried you suggestion, seems not working Matt.
Matt J
Matt J 2014-10-27
编辑：Matt J 2014-10-27
Means little. You haven't shown us what you've actually done. You haven't shown what you've actually observed.
VISWANATH
VISWANATH 2014-10-28
When i used
[R, fval, exitflag] = lsqnonlin(@(x)err(x),complex(2.11,-0.064) )
gave the best values for fit but solution did not converge!!! Where do you think i am going wrong?
R =
2.1151 - 0.0640i
fval =
1.6100e-04
exitflag =
0.0127
Matt J
Matt J 2014-10-28
The objective function must be a mapping from reals to reals. The initial guess x0 must also be real. So, complex(2.11,-0.064) is not legal as an initial point.

请先登录，再进行评论。

VISWANATH
VISWANATH 2014-10-29

0 个投票

Hi Matt, It looks like the following example may help me to solve my problem. If you have any suggestions i would be glad to hear from you. Thanks a lot. Fit a Model to Complex-Valued Data

类别

在 帮助中心 和 File Exchange 中查找有关 Solver Outputs and Iterative Display 的更多信息

标签

提问:

VISWANATH
VISWANATH
2014-10-23

回答：

VISWANATH
VISWANATH
2014-10-29

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by