How to show every iteration step of lsqnonlin()?

Question

Nico Lange 2020-12-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/676453-how-to-show-every-iteration-step-of-lsqnonlin

评论： Nico Lange 2020-12-4

Hello again,

I am solving a nonlinear compensation problem on a cirlce. So first i am creating 10 points randomly.

phi1=1:((2*pi/10.71)):2*pi;
r = -0.5 + (0.5 + 0.5) * rand(1,10);  
xrand = sin(phi1) + 0.25 * r;              
yrand = cos(phi1) + 0.25 * r;               
figure (1)                              
sz = 80;                                
scatter(xrand,yrand,sz,'ob','linewidth',1);    
axis ([-1.5 1.5 -1.5 1.5]);
grid on;
hold on

After that, I am using lsqnonlin to solve the equation for a circle and plot the result with the 10 points.

f=@(x)((xrand-x(1)).^2+(yrand-x(2)).^2-x(3).^2)';
x0=[0,0,1];                       
KreisFit1 = lsqnonlin(f,x0);        
                                     
figure (1)                             
phi = linspace(0,2*pi,100);             
xFit1 = KreisFit1(3)*cos(phi) + KreisFit1(1); 
yFit1 = KreisFit1(3)*sin(phi) + KreisFit1(2); 
plot(xFit1,yFit1,'b-','linewidth',3)
hold off

I also want to show every step of the iteration done by lsqnonlin in the same figure.

How can i visualize each Step of the iteration?

Thanks for every help :)

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Answer 1

Steven Lord 2020-12-3

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https://ww2.mathworks.cn/matlabcentral/answers/676453-how-to-show-every-iteration-step-of-lsqnonlin#answer_564508

You probably want to specify a PlotFcn as part of the options that get passed into lsqnonlin. See this documentation page for more information.

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Steven Lord 2020-12-3

在 MATLAB Online 中打开

example676453.m

options = optimoptions(@lsqnonlin,'Display','iter-detailed','MaxfunEvals',35);

You did not specify that you wanted lsqnonlin to use a PlotFcn. Consider something along the lines of the attached.

Nico Lange 2020-12-4

在 MATLAB Online 中打开

Sorry, the example didn't really helped. But i understood what you mean with PlotFcn. I've tried it like this

options = optimoptions(@lsqnonlin,'Display','iter','OutputFcn',@outfun);
[x,resnorm,residual,exitflag,output] = lsqnonlin(f,x0,[],[],options);
function stop = outfun(xrand,yrand,state)
        stop=false;
        switch state
            case 'iter'
                figure (1);
                hold on;
                grid on;
                plot(xrand,yrand,'ko')
                plot(xrand,((xrand-x(1)).^2+(yrand-x(2)).^2-x(3).^2), 'r');
                hold off
            case 'interrupt'
            case 'init'
            case 'done'  
            otherwise
        end
    end 