why my deeplearning toolbox can not work

My Matlab R2018b have Deeplearning Toolbox ,and I can see it using 'ver'.But when I use 'alexnet' Matlab says error.

I searched the 'alexnet.m' file is in my MATLAB\toolbox\nnet\cnn. But it also can not work.

Answer 1

[Stephan]

you have to install the pretrained Networks seperatly. Use the Add on Manager.

[Shaonong]

ohhhhhhh,I did it.thanks soooo much. Although I don't know how to show my super-thank in English,but in Chinese it is 小哥哥超级感谢你哒，感谢你解救我于水火之中，