This recipe will go over basics of plotting mathematical functions and several things that are related to math graphs such as writing Greek symbols in labels and on curves.
The most common graph we will use is the line plot command, which draws the given (x,y) coordinates on a figure plot.
We start with computing sine and cosine functions over the same linear interval—from Pi to Pi with 256 points in between and we plot the values for sin(x) and cos(x) over the same plot as shown here:
import matplotlib.pyplot as pl import numpy as np x = np.linspace(-np.pi, np.pi, 256, endpoint=True) y = np.cos(x) y1 = np.sin(x) pl.plot(x,y) pl.plot(x, y1) pl.show()
That will give us the following graph:
Following this simple plot, we can customize more to give more information and be more precise about axes and boundaries as shown here:
from pylab import *
import numpy as np
# generate uniformly distributed
# 256 points from -pi to pi, inclusive
x = np.linspace(-np.pi, np.pi, 256, endpoint=True)
# these are vectorised versions
# of math.cos, and math.sin in built-in Python maths
# compute cos for every x
y = np.cos(x)
# compute sin for every x
y1 = np.sin(x)
# plot cos
plot(x, y)
# plot sin
plot(x, y1)
# define plot title
title("Functions $sin$ and $cos$")
# set x limit
xlim(-3.0, 3.0)
# set y limit
ylim(-1.0, 1.0)
# format ticks at specific values
xticks([-np.pi, -np.pi/2, 0, np.pi/2, np.pi],
[r'$-pi$', r'$-pi/2$', r'$0$', r'$+pi/2$', r'$+pi$'])
yticks([-1, 0, +1],
[r'$-1$', r'$0$', r'$+1$'])
show()That should give us a slightly nicer graph:
We see that we used expressions such as $sin$ or $-pi$ to write letters of the Greek alphabet in figures. This is LaTex syntax, which we will explore further in the following chapters. Here, we just illustrated how easy it is to make your math charts more readable for certain audiences.