StarDestroyer.Net BBS

I'm trying to do something and I may have bitten off more than I can chew. My dad asked me if I could create a graphical representation of an economical model he developed, which breaks supply and demand down to consumption demand and production supply (the neo-classical model), inventory demand and supply, and sales demand and supply. Three graphs that interact with each other.

Now, the model itself is too mathematically complex for me to understand, but he just wants me to "fake it" by giving arbitrary values to make the curves look right, and then (this is the hard part) making the other curves shift into a new equilibrium when one of them changes.

I originally thought I could do it with Excel, but Excel has no awareness of when curves are intersecting and it can't draw a vertical line on a graph. Can someone suggest a free and hopefully easy to use graphing package for Windows or Linux that might fit the bill? Or is what I ask impossible, and will I have to (re)learn to code? If so, what programming language can do something like this and not take too long to learn?

I'd like to be able to do this within the next couple of weeks, if possible, so nothing so complex that it would take that long just to learn the ins and outs.

Doesn't OpenOffice.org have a program that features this ability? Since it's basically an open source equivalent to MS Office.

I already have MS Office, so that's not an issue. But I don't know of any way for Excel to draw a vertical line on a graph, or to shift a curve so that it intersects.

Are you using the X-Y chart option in Excel? I've been able to generate vertical lines without any trouble.

No, I guess not. I'm good at doing certain things in Excel, but my knowledge of it overall is rather limited. Anyway, I'm wondering if I'm not overthinking this. The purpose of all this is to illustrate the model to students and to colleagues at presentations so they can understand it. Maybe the best way would be to use Powerpoint animations and draw the graphs by hand?

MathCAD might do this (or Maple, Mathematica, etc.)

That said, Excel should be able to do this for you - learn how to use the plotting system. You could, say, have an arbitrary number of datapoints (20?) with the first column representing x and the next columns representing y for various functions. Additional cells will represent differing constants in your functions.

Quick way to do a vertical line on Excel is to have two pairs of numbers, so that they both have the same x-coordinate, but different y-coordinates. Then use them to create an x-y scatter plot, choose one that joins the dots, and voila!

Cool. Thanks for the tips!