checkGradients, but the objective function has two inputs: x and xdata?

Question

Benjamin Pepper 2024-11-14，10:21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2166278-checkgradients-but-the-objective-function-has-two-inputs-x-and-xdata

评论： Benjamin Pepper about 3 hours 前

I'm using lsqcurvefit with the following objective function and Jacobian:

function [f, jacF] = semiCircle(p, Q)
P0 = p(1);
Q0 = p(2);
r = p(3);
f = P0 + sqrt(r^2 - (Q-Q0).^2);
if nargout > 1 % need Jacobian
    jacF = [1, (Q-Q0)./sqrt(r^2-(Q0-Q).^2), r./sqrt(r^2-(Q0-Q).^2)];
end
end

I'd like to use checkGradients to verify if the Jacobian is correct. However, all of the examples in the documentation just have objective functions with one input, the parameters 'x'. Whereas my function semiCircle has two inputs: the parameters 'p' and the xdata 'Q'. Is there a way to use checkGradients for such a function?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Torsten 2024-11-14，10:31

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2166278-checkgradients-but-the-objective-function-has-two-inputs-x-and-xdata#answer_1545231

在 MATLAB Online 中打开

valid = checkGradients(@(p)semiCircle(p, Q),p0)

9 个评论
显示 7更早的评论隐藏 7更早的评论

Benjamin Pepper about 4 hours 前

在 MATLAB Online 中打开

Here's the code and attachments:

load('data.mat')
Vb_ll_rms = 690;
% Inital guess
p10 = 5e6;
p20 = 2.5e7;
p30 = 3e7;
p0 = [p10, p20, p30];
[Rls, Xls, Vgls, gradientCheck] = lsqcurvefitNLS(p0, Q, P, Vb_ll_rms)
Rls = 0.0024
Xls = 0.0238
Vgls = 689.9365
gradientCheck = logical
   1

lsqcurvefirNLS calls lsqcurvefit with box and linear constraints, which in turn calls the semiCircle function. Rls, Xls, and Vgls are the estimated parameters, and gradientCheck verifies the objective gradient given.

Here, the code runs fine. However, in my desktop MATLAB it returns the following error:

Error using  - 
Too many output arguments.
Error in lsqcurvefit>@(X)feval(FUN,X,XDATA)-YDATA (line 237)
[xCurrent,Resnorm,FVAL,EXITFLAG,OUTPUT,LAMBDA,JACOB] = cnls(caller, @(X) feval(FUN, X, XDATA) - YDATA,...
    
Error in cnls/funExt (line 355)
[Fvec,JACOBIAN] = feval(FUN, Xk);                    
Error in cnls/objective (line 319)
[f,F] = funExt(xIn);
Error in cnls>@(x)objective(x,true) (line 188)
fungrad = @(x) objective(x, true);
Error in fmincon (line 598)
initVals.g = feval(funfcn{4},X,varargin{:});
Error in cnls (line 215)
[X,~,EXITFLAG,OUTPUT,LAMBDA] = fmincon({fun,fungrad},X(:),...
    
Error in lsqcurvefit (line 237)
[xCurrent,Resnorm,FVAL,EXITFLAG,OUTPUT,LAMBDA,JACOB] = cnls(caller, @(X) feval(FUN, X, XDATA) - YDATA,...
    
Error in lsqcurvefitNLS (line 19)
p = lsqcurvefit(@semiCircle, p0, Q, P, lb, ub, A, b, [], [], [], options);
Caused by:
Failure in initial objective gradient function evaluation. FMINCON cannot continue.
lsqcurvefit cannot continue.

This might be because there are square-root terms in the Jacobian/objective gradient which are maybe giving complex values:

jacF(i,:) = [1, (Q(i)-Q0)/sqrt(r^2-(Q0-Q(i))^2), r/sqrt(r^2-(Q0-Q(i))^2)]

However, the linear contraints are designed to prevent the solution from entering that region. And, the code seems to run here online without any problems.

I could try updating my MATLAB to the 2024b version?

Torsten about 4 hours 前

Could you include the .m-files instead of the .mlx-files ?

Benjamin Pepper about 3 hours 前

在 MATLAB Online 中打开

I reached my daily uploads limit, so I'll just put the functions here:

function [R, X, Vg, gradientCheck] = lsqcurvefitNLS(p0, Q, P, Vo)
% Box constraints
p1_ub = min(P);
p2_lb = max(Q);
p3_lb = max(Q) - min(Q);
lb = [0, p2_lb, p3_lb];
ub = [p1_ub, inf, inf];
% Linear constraints
A = [0, 1, -1];
b = min(Q); 
gradientCheck = checkGradients(@(p)semiCircle(p,Q),p0);
options = optimoptions('lsqcurvefit','Display','off','SpecifyObjectiveGradient',true);
p = lsqcurvefit(@semiCircle, p0, Q, P, lb, ub, A, b, [], [], [], options);
P0 = p(1);
Q0 = p(2);
r = p(3);
R = P0/(P0^2 + Q0^2)*Vo^2;
X = Q0/(P0^2 + Q0^2)*Vo^2;
Vg = sqrt(r^2/(P0^2 + Q0^2)*Vo^2);

And the other one:

function [f, jacF] = semiCircle(p, Q)
P0 = p(1);
Q0 = p(2);
r = p(3);
f = P0 + sqrt(r^2 - (Q-Q0).^2);
if nargout > 1 % need Jacobian
    jacF = zeros(length(Q), length(p));
    for i = 1:length(Q)
        jacF(i,:) = [1, (Q(i)-Q0)/sqrt(r^2-(Q0-Q(i))^2), r/sqrt(r^2-(Q0-Q(i))^2)];
    end
end

请先登录，再进行评论。

checkGradients, but the objective function has two inputs: x and xdata?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

9 个评论
显示 7更早的评论隐藏 7更早的评论

更多回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

checkGradients, but the objective function has two inputs: x and xdata?

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

9 个评论 显示 7更早的评论隐藏 7更早的评论

更多回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

9 个评论
显示 7更早的评论隐藏 7更早的评论