creating a function getting the graident and passing variables to them

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Nora Khaled 2019-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/449447-creating-a-function-getting-the-graident-and-passing-variables-to-them

评论： Nora Khaled 2019-3-11

采纳的回答： Alex Mcaulley

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Hi !

I am trying to creat a function that I can both use to pass values and compute the gradient of that function.

I tried both these :

but the for the first I cant pass values and the 2nd the gradient function in matlab does not work

syms x1 x2
f= 100*(x2-x1^2)^2 + (1+x1)^2;
gr= gradient(f)
%%%%%% other way 
syms x1 x2 
f=@(x1,x2) 100*(x2-x1^2)^2 + (1+x1)^2;
gr= gradient(f)

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Geoff Hayes 2019-3-11

Nora - please clarify what you mean by but the for the first I cant pass values and the 2nd the gradient function in matlab does not work. What do you mean by this? Are you observing errors? If so, what are they?

Nora Khaled 2019-3-11

yes there were some error when I try to do f(2,3) for example and the second one had error related to the gradient function not accepting a function was created using f=@(x,y).

but it currntly works using what was suggested in the answers.

thank you !

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Answer 1

Alex Mcaulley 2019-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/449447-creating-a-function-getting-the-graident-and-passing-variables-to-them#answer_364849

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Is this that you want?

syms f(x1,x2)
f(x1,x2)= 100*(x2-x1^2)^2 + (1+x1)^2;
gr(x1,x2) = gradient(f,[x1,x2])

Then you can compute

f(0,0)
gr(0,0)

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Nora Khaled 2019-3-11

Thank you this work.

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creating a function getting the graident and passing variables to them

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