If there is a method to define the size of unknown vector x rather than this ???

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M.Shaarawy 2018-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/384563-if-there-is-a-method-to-define-the-size-of-unknown-vector-x-rather-than-this

回答： Steven Lord 2018-2-26

采纳的回答： John D'Errico

I want to define the size of x vector, rather than this.. x=sym('x%d%d', [27 1]) where my size is 27*1

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Answer 1

John D'Errico 2018-2-24

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编辑：John D'Errico 2018-2-24

在 MATLAB Online 中打开

x = sym('x',[27,1]);

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Karan Gill 2018-2-26

Post your full code and data. Your question is not clear otherwise. If you get an error, try a search for the error message to understand what is happening.

M.Shaarawy 2018-2-26

function y = simple_fitness(x) load A.mat; % 27*27 matrix load obs.mat; % 27*1 vector y=norm(A*x-obs,2);

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Answer 2

Steven Lord 2018-2-26

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If you're passing a function handle to costfun into some optimizer, you don't have to create x in your code (and you should not do so.) The optimizer will pass an x it has created into your function as the input argument and you just need to use it.

As an efficiency note, I would avoid calling load inside your objective function. Your objective function is likely to be called many times and all that disk access will take time. Call load twice outside the function and pass the variables you loaded into your objective function as extra parameters using one of the techniques described on that documentation page.