True for Handle Graphics object handles
ishghandle(h) returns an array that contains 1's where the elements of h are handles to existing graphic objects and 0's where they are not. Differs from ishandle in that Simulink® objects handles return false.
Create a plot and find the valid handles:
x = [1:10]; y = [1:10]; p=plot(x,y); ishghandle([x y p]) % This returns a 1-by-21 array of values with ones at the first, % eleventh, and last values, if the figure handle is 1.