Python - Plot function over a range PYPLOT

Question

If I have a function

def function(self, x, A, B)
   ......

How can I plot a continuous graph of it over a range of say x=[0,150000] (A/B are constants and can be changed on each call).

Even discrete values is fine. However it is inefficient to make a list of all function values then plot each one?

Your question is not very clear here. Plotting is always discrete. There are just way too many numbers in a closed interval of real numbers :) — cel
– cel, Commented Aug 11, 2015 at 8:26

Amy Teegarden · Accepted Answer · 2015-08-11 20:28:27Z

3

I'm assuming you mean the function is going to be some kind of mathematical function, for example:

import math
def function(x, A, B):
    return math.exp(A*x) * math.sin(B*x)

Then I would define variables for the number of points to plot, and the x range, and then create lists using map, as below.

import matplotlib.pyplot as plt
points = 1e4 #Number of points
xmin, xmax = -1, 5
xlist = map(lambda x: float(xmax - xmin)*x/points, range(points+1))
ylist = map(lambda y: function(y, -1, 5), xlist)
plt.plot(xlist, ylist)
plt.show()

edited Aug 11, 2015 at 20:28

Amy Teegarden

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answered Aug 11, 2015 at 13:15

Siwel

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3 Comments

Ankit Seth Over a year ago

I am getting error-

>>> xlist = map(lambda x: float(xmax - xmin)*x/points, range(points+1)) Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: 'float' object cannot be interpreted as an integer

Siwel Over a year ago

@Ankit Make sure the variable points is an integer (there can only be an integer number of points). The error comes from calling range with a non-integer argument. This answer was written for Python 2 where 1e4 is an integer, whereas it is a float in Python 3.

András Aszódi Over a year ago

Instead of xlist = map(lambda x: float(xmax - xmin)*x/points, range(points+1)) you may wish to use NumPy's linspace function: import numpy as np and then xlist = np.linspace(xmin, xmax, points)

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