Maple is a nice enough program, but it keeps me in a steady supply of WTF moments in the course of using it, and sometimes it does bizarre things that drive me up the wall. Here’s one I just can’t figure out. I’m trying to make a plot of y = 120 – e^(-0.2x). This graph should have a horizontal asymptote at y = 120. However, check out what I get from Maple:
What’s with the “99999” repeatedly on the y-axis?
Trying to debug, I changed the 120 to a 30:
…and the y-scaling is correct. But change the 30 to a 40 and I get:
There it is again, although it’s 99998 this time.
The critical value of the constant seems to be 32.919. Anything above that in the function yields 99998 all up and down the y-axis. Anything at that level or below gives the proper y-scaling.
Can somebody explain what’s up with that?
Technorati Tags: Computer algebra system, Maple, Graph
Casting Out Nines 
Somehow your view window is cutting off the leftmost portion of the number. It is not showing you that in fact your tick marks are at 118.9999999999, 119.24999999999, etc. If you can’t manage to get the window to expand further to the left and expose these numbers, you need to change the tickmarks, manually. You can do this with the tickmarks option in the plot command and tell it precisely where you want the tickmarks, for example,
plot(120.0-exp(-.2*x), x = 0 .. 20, tickmarks = [[0, 5, 10, 15, 20], [119, 119.5, 120]])
should get you what you want.