# This program will make plots in python, version 3+, using
# utilities from matplotlib and numpy.

# Always include these next two import commands.

import numpy as np
import matplotlib.pyplot as plt

# This shows how to define your own function.

def func(x):
    return np.sin(2*np.pi*x)

# ***** How to make a plot of data with error bars. ******

# Generate some fake data.

x1 = np.arange(10) + 2*np.random.randn(10)
y1 = np.arange(10) + 2*np.random.randn(10)

# Generate fake errors for the data.

x1err = 2*np.random.random(10)
y1err = 2*np.random.random(10)

# Make the plot.

plt.errorbar(x1, y1, xerr=x1err, yerr=y1err, fmt='bo')
plt.xlabel('X Data', labelpad=10)
plt.ylabel('Y Data', labelpad=10)
plt.title('Random Plot with Error Bars')
plt.show()

# ***** How to make a plot of multiple functions. *****

# Now make another plot with multiple plots on the same
# screen.

x2 = np.arange(1, 19, .4)
y2a = np.log10(x2)
y2b = 0.01 * x2**2
y2c = 0.9 * np.sin(x2)

plt.plot(x2, y2a, 'r-', label='y2a')
plt.plot(x2, y2b, 'b^', label='y2b')
plt.plot(x2, y2c, 'go', label='y2c')
plt.plot(x2, y2a+y2b+y2c, '+', label='y2a+y2b+y2c')
plt.legend(loc=2)
plt.show()

# ***** How to make more than one plot on a page. *****

# We'll make use of of the defined function `func' from
# the beginning of this Python program.

x3a = np.arange(0.0, 4.0, 0.1)
x3b = np.arange(0.0, 4.0, 0.01)

y3a = func(x3a)
y3b = func(x3b)
y3an = y3a + 0.1*np.random.randn(len(x3a))

plt.figure()  # Initialize the figure space.

# Make 2 plots vertically + 1 horizontally.
# Start with the first (upper left).

plt.subplot(211)

plt.plot(x3a, y3a, 'bo', x3b, y3b, 'r:')

plt.subplot(212)  # Now the 2nd (lower left) plot.

plt.plot(x3a, y3an, 'bo', x3b, y3b, 'r:')

plt.show()