How to use optimset in Matlab2018?

I was using Matlab2016 and everything was working. I have recently updated MATLAB and I got into this problem

itermax=1000;
options=optimset('MaxFunEvals',itermax,'MaxIter',itermax,'Display','off','TolFun',1e-6,'TolX',1e-6);
Undefined function or variable 'uselargeoptimstruct'.
Error in optimset (line 87)
optimtbx = uselargeoptimstruct;

[Walter Roberson]

That function has been at toolbox/matlab/optimfun/private/uselargeoptimstruct.m since at least R2012a .

You might need to reinstall the toolbox.

[LARAN CAS]

Which toolbox? I have the Optimization toolbox and I do not find any toolbox called optimfun.

[Walter Roberson]

optimfun is the directory used to store the Optimization Toolbox.

[RFAN MAHMO A]

how to reinstall this toolbox?

[Walter Roberson]

In the last 2 years or so you can use the Add-on Explorer to request that the toolbox be removed or installed.

Before that you would have to go into the installer and do a custom install in which you select just that product.