Evaluate in a single value a function matrix

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JORGE ORDOÑEZ CARRASCO 2020-12-29

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评论： JORGE ORDOÑEZ CARRASCO 2020-12-29

Hi i have a to program Newton Raphson in many variables so for example: If i have a function

just like

It is known the Jacobian of f will return in this case a matrix of 2x2. I need to evaluate

in a value for example u1=1 and u2=2. But f(1,1) obviously doenst work, i need to evaluate numerically this function and its jacobian and extend this for many variables above 2. By the way the jacobian is:

As you can see for example matrix A(1,1) returns element not a value so how can i evaluate a matrix and a vector in a known number without using x=rand(2,1), x(1),x(2) cause for many variables this will be more dificult to do it.

Thank you

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Answer 1

Walter Roberson 2020-12-29

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https://ww2.mathworks.cn/matlabcentral/answers/704682-evaluate-in-a-single-value-a-function-matrix#answer_586652

在 MATLAB Online 中打开

Use the Symbolic Toolbox to build the equations. Then use matlabFunction with the 'vars' option passing in a cell array that contains a single entry that is the vector of variable names. matlabFunction will then generate an anonymous function with all of the variables extracted from a single vector of inputs.

syms u1 u2
f = [exp(u1)-cos(u2); exp(u2)-u1^2];
fh = matlabFunction(f, 'vars', {[u1, u2]})
fh = function_handle with value:
    @(in1)[-cos(in1(:,2))+exp(in1(:,1));exp(in1(:,2))-in1(:,1).^2]