# looking for good free function plotting software

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There are some parameters in my game that I need to generate dynamically based on variables that represent various game state values. I think I have the function that I'm going to use worked out. It's based on the logistic function. (The function needs to be sigmoidal and I chose the logistic function more-or-less at random: seems like the easiest one to compute except maybe arctangent)

Anyway, I'm looking for a freeware application that plots functions to see if my math is correct. I want to be able to set up the function in terms of constants and have it plot the curve given various values for the constants.

Would Maxima do this easily? Or would I have to spend an entire day figuring out how to use it?

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Probably the most convenient thing is just Wolfram Alpha. Give it a try.

I use gnuplot.

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Sneftel, do you know how to put constants in there? I want to do something like

Plot[A/(1 + Exp[-(a * x + b)) + B]), {x, 0, 10}, {A = 1.0}, {B = 2.0}, {a = 3.0], {b = 4.0}]

or whatever, but I don't know the syntax.

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I ended up using Maxima. For the benefit of future googlers to get Maxima to plot a function in terms of constants, type in something like the following, hitting enter at the end of each line and shift-enter at the end of the whole thing:

V0: 1 $V1: 5$
m: 15 $h: 30$
H: 0.99 $A : V1 - V0$
B : V0 $a : log((1 - H) / H) / (m - h)$
b : m * log((1 - H) / H) / (h - m) \$

f(t) := A / (1 + exp(-(a * t + b))) + B;

plot2d(f, [t, 0, 30]);

Then just cut and paste and change the constants to see it with different values.

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Sage and gnuplot are both fairly good free ones as well.

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Quote:
 Original post by tabySage and gnuplot are both fairly good free ones as well.

Wow, Sage looks really nice. Thanks for the tip, hadn't heard about it before. So from reading the wikipedia article, it's a superset of Maxima's functionality?

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