Evaluate in a single value a function matrix
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Hi i have a to program Newton Raphson in many variables so for example: If i have a function
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/473467/image.png)
just like
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/473472/image.png)
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:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/473477/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/473482/image.png)
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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Answers (1)
Walter Roberson
on 29 Dec 2020
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]})
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Walter Roberson
on 29 Dec 2020
That is not my suggestion. I specifically said that you need to use the vars option with {} and I gave an example to emphasize what hasto be done .
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