if you type to the MATLAB Console
>> imshow
and it returns "not found"
then (AND ONLY THEN) do the followings:

on the MATLAB ribbon
- press "HOME"
    - press "Set Path"
	    - press "Add Folder"
		and select the following folder:
		C:\Program Files\MATLAB\R2016a\toolbox\matlab\images\
		then press "Select"
		then press "Save"
		
hopefully works from now