problem with fminunc: why the returned gradient is not a vector
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Hi, I am using the fminunc to find a minimum of a multivariable function f(x), where x is a vector. I want to know the value of the gradient at the solution x. So I type "[x,grad] = fminunc(fun,x0)" to get the gradient. However, the returned gradient is a scalar instead of a vector. I think the gradient should be a vector since my x is a vector. Could somebody explain it for me? Thanks!
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Answers (1)
Mischa Kim
on 4 Mar 2014
Edited: Mischa Kim
on 4 Mar 2014
Chuoxin, have you set
options = optimset('GradObj','on') % gradient outputted as 2nd argument
[x,fval,exitflag,output,grad] = fminunc(...) % gradient is 5th argument
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Matt J
on 4 Mar 2014
The gradient should always be returned in the 5th output argument, even when GradObj option is used.
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