I don't know what is an "equalization histogram", but searching for it shows most hits for the more familiar " histogram equalization" which isn't a graph but an operation done on an image. Unless you talk about the cumulative distribution function graph (as shown in this applet)?

And I found no significant search result for "discrete case histogram" (supposing it is "discrete", not "descrete").

So perhaps you should be more precise in your request. Showing your current code might help too.

Perhaps this is what you mean:  http://en.wikipedia.org/wiki/Histogram_equalization#Full-sized_image