update on getting started

doc/src/How2ReadData/src/Hudson_Bay.py~

@@ -0,0 +1,43 @@
+import numpy as np
+import matplotlib.pyplot as plt
+
+def solver(m, H0, L0, dt, a, b, c, d, t0):
+    """Solve the difference equations for H and L over m years
+    with time step dt (measured in years."""
+
+    num_intervals = int(m/float(dt))
+    t = np.linspace(t0, t0 + m, num_intervals+1)
+    H = np.zeros(t.size)
+    L = np.zeros(t.size)
+
+    print 'Init:', H0, L0, dt
+    H[0] = H0
+    L[0] = L0
+
+    for n in range(0, len(t)-1):
+        H[n+1] = H[n] + a*dt*H[n] - b*dt*H[n]*L[n]
+        L[n+1] = L[n] + d*dt*H[n]*L[n] - c*dt*L[n]
+    return H, L, t
+
+# Load in data file
+data = np.loadtxt('Hudson_Bay.csv', delimiter=',', skiprows=1)
+# Make arrays containing x-axis and hares and lynx populations
+t_e = data[:,0]
+H_e = data[:,1]
+L_e = data[:,2]
+
+# Simulate using the model
+H, L, t = solver(m=20, H0=34.91, L0=3.857, dt=0.1,
+                 a=0.4807, b=0.02482, c=0.9272, d=0.02756,
+                 t0=1900)
+
+# Visualize simulations and data
+plt.plot(t_e, H_e, 'b-+', t_e, L_e, 'r-o', t, H, 'm--', t, L, 'k--')
+plt.xlabel('Year')
+plt.ylabel('Numbers of hares and lynx')
+plt.axis([1900, 1920, 0, 140])
+plt.title(r'Population of hares and lynx 1900-1920 (x1000)')
+plt.legend(('H_e', 'L_e', 'H', 'L'), loc='upper left')
+plt.savefig('Hudson_Bay_sim.pdf')
+plt.savefig('Hudson_Bay_sim.png')
+plt.show()

doc/src/How2ReadData/src/plot_Hudson.py~

@@ -0,0 +1,19 @@
+import numpy as np
+from  matplotlib import pyplot as plt
+
+# Load in data file
+data = np.loadtxt('src/Hudson_Bay.dat', delimiter=',', skiprows=1)
+# Make arrays containing x-axis and hares and lynx populations
+year = data[:,0]
+hares = data[:,1]
+lynx = data[:,2]
+
+plt.plot(year, hares ,'b-+', year, lynx, 'r-o')
+plt.axis([1900,1920,0, 100.0])
+plt.xlabel(r'Year')
+plt.ylabel(r'Numbers of hares and lynx ')
+plt.legend(('Hares','Lynx'), loc='upper right')
+plt.title(r'Population of hares and lynx from 1900-1920 (x1000)}')
+plt.savefig('Hudson_Bay_data.pdf')
+plt.savefig('Hudson_Bay_data.png')
+plt.show()