#! /usr/bin/env python

# plot4.py
#
# Example python program introducing the use 
# of the matplotlib module to plot multiple subplots
# in a single figure.
#
# Paul Eugenio
# PHZ4151C
# Jan 28, 2019
#

import matplotlib.pyplot as plt 
plt.rc('text', usetex=True)

import numpy as np



def cross_section(t, b):
    """  
    The transverse four-momentum scattering cross section:  t * exp(-t)
    """
    return (t-b)**2 * np.exp(-t)


#
# generate an array of values to plot
#
x = np.linspace(0,10,101)
b = 0
y = cross_section(x,b)

# create a figure with 2 subplots setting 
# the plotting to the first subplot 
fig = plt.figure()
plt.subplot(211)

# plot data and dress figure
plt.plot(x,y)
plt.title("Scattering Probability")
plt.xlabel("t")
plt.ylabel("\sigma(t,b) = t^2 e^{-t}")

# generate additiional data to plot
b = 1
y = cross_section(x,b)

# change plotting to the second subplot
plt.subplot(223)

# plot data and dress figure
plt.plot(x,y)
plt.xlabel("t")
plt.ylabel("\sigma(t,b) = (t-1)^2 e^{-t}")

plt.savefig("sigma-stack.png")

fig.show()

raw_input("Enter [return] to exit.")