How to add a figure into PPT by using MATLAB script?

I have trouble to add figure into a PPT with MATLAB scripts:

% --------------------

import mlreportgen.ppt.*

slides = Presentation('my_test');

add(slides,'Title Slide');

add(slides,'Title and Picture');

contents = find(slides, 'Title');

replace(contents(1),'My First Presentation');

contents(1).FontColor = 'red';

x = [0 1 2 3 4 5];

y =[6 7 8 9 10 11];

zrh = plot(x, y); hold on; grid on;

contents = find(slides, 'Picture');

add(contents(1),zrh);

close(slides);

% ---------------

After this, I opened the PPT file "my_test" and there is no figure in it.