Error code : Error using optimoptions (line 105)?

when I enter the following command :

options = optimoptions('fminunc','Algorithm','trust-region','SpecifyObjectiveGradient',true);

Matlab displays the following error :

Error using optimoptions (line 105)
'SpecifyObjectiveGradient' is not an option for FMINUNC.
A list of options can be found on the FMINUNC documentation page.

I don't know this origin?

Thanks!

Answer 1

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/289912-optimizing-with-user-specified-gradients#answer_225530

[amine&&]

Thanks Roberson!