Help with patch

Hello, i need your help to understand how patch works. I have made a 2D plot in matlab and i would like to add some patches to it. I use the following commands

xpatch=[340.04 340.07;340.04 340.07]; % create x axis patch area
ypatch=[0 1600;0 1600]; % create y axis patch area
patch(xpatch,ypatch,'r');

my problem is that even if the patch object has been created in the plot brower of the figure window, it isn't visible in my figure. I would appreciate any help

Thank you

Answer 1

[Walter Roberson]

Do not use 2D arrays for the patch coordinates: patch() wants vector lists of coordinates for each patch.

xpatch = [340.04 340.07 340.07 340.04 340.04];
ypatch = [0 0 1600 1600 0];
patch(xpatch,ypatch,'r')

The point order is important here, as are the seeming duplications.

[Andrew Newell]

The fifth elements in xpatch and ypatch aren't needed.

[Andrew Newell]

The reason for the point order is that you must give the points in the order you are traversing the patch, e.g, [xpatch(1) ypatch(1)] to [xpatch(2) ypatch(2)] ...

[Walter Roberson]

I prefer not to count upon patch() automatically closing the patch.

[Kostas]

Thanks a lot for the help, it worked fine when i created the same plot from the beginning

Answer 2

[Kostas]

Thanks for your answers, i have made the proposed alterations but i still get the same result, as can be seen in the following image

http://imageshack.us/photo/my-images/713/patchn.png/

[Jonathan Sullivan]

It works for me. Make sure you use the hold on command before trying to pot anything else on top.