not sure a simple solution to an extremely complex problem will actually be useful, but the excercise can be. I have worked extensively on this problem and have found it to be a fascinating study that has helped my game tremendously.

First of all, the villian's stack ratio in relation to that of hero's is actually less of a factor when calling off their stack than the their ratio in relation to the blinds. Villian can have <.5 of Hero's stack and still not be desperate in relation to the blinds or other stacks.

I also think you have to at least find a simple model that identifies your image. Even just whether or not the table perceives you as "desperate".

But in the end, without a vastly more complex model, I think you will find the results to be quite inaccurate.