Error: Not enough input arguments.

Question

Ba Ba Black Sheep! 2017-1-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/318846-error-not-enough-input-arguments

评论： Walter Roberson 2017-1-3

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

The following code works fine.

See the inline function fungrad.

 function [x, fval, eflag, iter, fcount] = 
          Optimization_With_Analytic_Gradient(start_point)
    x0 = start_point;
    %   inline function defitions
    fungrad = @(x)deal(fun(x),grad(x));
    % options setup
    options = optimoptions( 'fminunc', ...
                            'Display','off',...
                            'OutputFcn',@bananaout,...
                            'Algorithm','trust-region', ...
                            'GradObj','on');
    % calling fminunc
    [x,fval,eflag,output] = fminunc(fungrad,x0,options);
    iter = output.iterations;
    fcount = output.funcCount;
    %   plot window title
    title 'Rosenbrock solution via fminunc with gradient'    
    disp('Optimization_With_Analytic_Gradient...');
end

But, when I call it using the following code,

 function out = fungrad(x)
     out = deal(fun(x),grad(x));
 end

It displays the following error:

 Error using fungrad (line 2)
 Not enough input arguments.
 Error in Optimization_With_Analytic_Gradient (line 24)
    [x,fval,eflag,output] = fminunc(fungrad,x0,options);
 Error in main (line 48)
        [x, fval, eflag, iter, fcount] = 
    Optimization_With_Analytic_Gradient(starting_point);

Rest of the code:

 function out = fun(x)
     out = 100*(x(2) - x(1)^2)^2 + (1 - x(1))^2;
 end
 function out = grad( x )
     out = [-400*(x(2) - x(1)^2)*x(1) - 2*(1 - x(1)); 
            200*(x(2) - x(1)^2)];
 end

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Answer 1

Walter Roberson 2017-1-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/318846-error-not-enough-input-arguments#answer_249205

在 MATLAB Online 中打开

[x,fval,eflag,output] = fminunc(@fungrad,x0,options);

However, your code will not work. Your objective function must return the gradient information only when nargout > 1. Your use of deal() always returns two outputs, and that is going to fail.

Refer to http://www.mathworks.com/matlabcentral/answers/318706-problem-running-fmincon-input-arguments-to-function-include-colon-operator#comment_417378

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Ba Ba Black Sheep! 2017-1-3

编辑：Ba Ba Black Sheep! 2017-1-3

在 MATLAB Online 中打开

 Your objective function must return the gradient information 
 only when nargout > 1.

which one? banana? or, fungrad?

_

N.B. Sorry! I am absolutely new.

Walter Roberson 2017-1-3

在 MATLAB Online 中打开

You have

fungrad = @(x)deal(fun(x),grad(x));

so your fungrad is always returning two outputs. fungrad is being used as your objective function for fminunc . The objective function must only assign the gradient when it is asked to do so. See the example https://www.mathworks.com/help/optim/ug/fminunc.html#butzm_r-1 and notice that it tests nargout

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