calculate the gradient f=@(x) (x(1)-2)^4+(x(1)-2)^2*x(2)^2+(x(2)+1)^2

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siscovic 2017-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/366431-calculate-the-gradient-f-x-x-1-2-4-x-1-2-2-x-2-2-x-2-1-2

回答： Star Strider 2017-11-11

采纳的回答： Star Strider

Hello, how to calculate the gradient, Hessian matrix, of this function.Thank you

f=@(x) (x(1)-2)^4+(x(1)-2)^2*x(2)^2+(x(2)+1)^2

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Answer 1

Star Strider 2017-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/366431-calculate-the-gradient-f-x-x-1-2-4-x-1-2-2-x-2-2-x-2-1-2#answer_290547

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With the Symbolic Math Toolbox:

syms x1 x2 
% f=@(x) (x(1)-2)^4+(x(1)-2)^2*x(2)^2+(x(2)+1)^2;
f = (x1-2)^4+(x1-2)^2*x2^2+(x2+1)^2;
Hf = hessian(f);
HF1 = matlabFunction(Hf, 'Vars', [x1 x2]);
HF2 = matlabFunction(Hf, 'Vars', {[x1 x2]});

The â€˜HF1â€™ result returns a function of (x1,x2). The â€˜HF2â€™ result returns a function of â€˜in1â€™, where â€˜in(:,1)=x1â€™ and â€˜in(:,2)=x2â€™. Note that â€˜in1â€™ is a row vector.