Where has this software been all my life?


graphsketcher_20070709112905.jpg I stumbled upon an amazing find a few minutes ago: an OS X application called Graph Sketcher. It is developed and maintained by MIT, and very simply, Graph Sketcher lets you hand-draw graphs on a set of coordinate axes and then manipulate them by changing color and thickness, shading in areas underneath, and so on. You can add text annotations to the graphs and (apparently, haven’t tried this yet) graph spreadsheet data and add best-fit lines.

Why this software blows my mind should be clear to anybody who’s ever had to make up a handout, test, or lab for calculus or precalculus. In doing those course preps, you are constantly needing to make up graphs that have a certain look — inflection points in a specified place, strange asymptotic behavior, jump discontinuities, even just basic piecewise functions. You know how the graph ought to look, but to get the graph, you had to come up with a formula for it, plot it in a computer algebra system, and then export the plot as PDF or a graphics file and then import it into your document. This process is alternately impossible or maddeningly time-consuming. Or you could try to freehand it in a paint program, but those programs aren’t meant for precision, and while you might be able to get the behavior right, the result looks like crap.

But this software lets you just draw the lines where you want them, and then bend them using simple Bezier curve handles. Or you can tell it to plot certain points and connect the dots. Here’s a plot I just drew for a quiz:

lab-8-quiz-plot.png

I just drew four connected line segments for the curve and then bent them around until I got what I wanted. Voila — instant logistic function with a y-intercept at 2 and carrying capacity at 10. I didn’t have to diddle around with y = \frac{A}{1 + Be^{-cx}} until I was blue in the face. (Even had I been inclined to do so, Maple still doesn’t work under Leopard so it’s moot.) Then one-click export to PDF, and I’m done. How many weeks might have been added back into my life that were otherwise wasted trying to get graphs to turn out right using formulas?

Best of all — it’s shareware. Who says there’s no good software out there for Macs?

3 Comments

Filed under Apple, Calculus, Math, Teaching, Technology

3 responses to “Where has this software been all my life?

  1. Oh my – I think I’m in love with this program. Thank-you!

  2. Ben Chun

    Wow, I have definitely had a need for this program. I’m really glad you found it for us!

    The only thing that strikes me as being a bit off is that the software is not designed or maintained “by MIT”. Although Apple’s download site has the company listed as “Massachusetts Institute of Technology”, these words link to graphsketcher.com which is owned by one Robin Stewart. Now, he’s a grad student at MIT, so it’s not like there’s no connection at all. But…

    If he is representing the software as being created by MIT when the licensing fees go into his pocket, he might have legal trouble on his hands. Given MIT’s long history of developing and supporting free software, I was certainly surprised to see this listed as shareware. That’s what made me look a little deeper.

  3. Indeed, it’s not shareware any more — there’s a demo period and then you must pay a licensing fee ($10 for educational licenses, $30 otherwise) and MIT is certainly not the sponsor of the software.

    It sounds like perhaps the software was originally free and under the auspices of MIT when it was first made available for download at Apple’s site. But now I guess the main developer has taken it commercial, and Apple hasn’t updated the info. Somebody probably ought to let Apple know about all this.

    Still, $10 is a lot less than the software is worth for me at least.