Plotting 2 or more functions in the same graph

Question

I would like to plot 2 curves in the same figure with the following code:

import sympy as syp


x, y = syp.symbols('x, y')

my_function = syp.exp(-(x-2)**2)*syp.exp(-(y-3)**2) + 2*syp.exp(-(x+1)**2)*syp.exp(-(y-1)**2) 

gradient_1 = syp.diff(my_function, x)
gradient_2 = syp.diff(my_function, y)


curve_1 = syp.plot_implicit(syp.Eq(gradient_1, 0))
curve_2 = syp.plot_implicit(syp.Eq(gradient_2, 0))

What I see is only the first plot, while I would like to have both the curves in the same picture, maybe also with a grid if possible. Any ideas?

_{Note: with matplotlib it's very easy, but I cannot find any specific example for the function syp.plot_implicit}

score 7 · Answer 1 · answered Nov 12 '13 at 22:45

7

Another, perhaps more efficient way, would be to compute both at the same time using Or

plot_implicit(Or(Eq(gradient_1, 0), Eq(gradient_2, 0)))

answered Nov 12 '13 at 22:45

asmeurer

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is this still the best way to go about this or have things changed? – baxx Nov 22 '15 at 16:58

score 3 · Accepted Answer · answered Nov 12 '13 at 15:34

3

It might work if you do:

>>> curve_1.extend(curve_2)
>>> curve_1.show()

However mixing implicit plots might not be implemented yet.

Be aware that your curve_1 and curve_2 are not what sympy considers "single curves" i.e. Series instance, but rather "collections of a number of curves", i.e. Plot instances.

You can also extract the matplotlib objects from curve_1._backend.fig and other _backend attributes.

In conclusion, there is a nice API to do what you want, but probably the methods behind it are not finished yet.

answered Nov 12 '13 at 15:34

Krastanov

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Yes, it works, that's great! I also found another way by using "pyplot.contour" (see [here](http://stackoverflow.com/questions/2484527/is-it-possible-to-plot-implicit-equations-using-matplotlib) ), but it requires the manual calculation of the gradient, so your method is still the best one. Do you know if it can be plotted with a grid? I don't see this option in the parameters that can be passed to the function... – user2983638 Nov 12 '13 at 15:52

Jeremy Anifacc · Answer 3 · 2017-10-18T09:00:29.283

0

Another way:

curve_1.append(curve_2[0]) curve_1.show()

edited Oct 18 '17 at 09:00

answered Oct 18 '17 at 08:49

Jeremy Anifacc

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Plotting 2 or more functions in the same graph

3 Answers3