"""
This code will run a matplotlib animation "live",
i.e. simply draw the plots on the screen in
sequence, with a short pause between to make the
movie look right. """

import numpy as np
import matplotlib.pyplot as plt

#the Gauss function
def f(x, m, s):
    return (1.0/(np.sqrt(2*np.pi)*s))*np.exp(-0.5*((x-m)/s)**2)


m = 0    #midpoint of curve

"""
We will animate how the curve changes shape as s goes from
2 to 0.2, so we create an array of s values in this interval:
"""
s_start = 2
s_stop = 0.2
s_values = np.linspace(s_start,s_stop,20)


x = np.linspace(-3*s_start,3*s_start,100)

#calculate the highest value  of f and fix the axes
f_max = f(m,m,s_stop)
plt.axis([-3*s_start,3*s_start,0,f_max])

y = f(x,m,s_start)

"""
We want to update the plot, so we keep the object return
from plt.plot in a variable:"""
lines = plt.plot(x,y)

#for loop over s values to update the y data and draw the plot
for s in s_values:
    y = f(x,m,s)
    lines[0].set_ydata(y)
    plt.draw()
    plt.pause(0.2)


"""
Terminal> python animate_gauss1.py
(output is an animation that will run once,
and then the plotting window is closed.)
"""