add figures

assets/img/figs/cubic.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+
+# Plots a cubic function and its root
+
+import numpy as np
+import scipy.optimize as opt
+import matplotlib.pyplot as plt
+
+
+def f(x):
+    return x**3 - x - 1
+
+def fprime(x):
+    return 3 * x**2 - 1
+
+def fprime2(x):
+    return 6 * x
+
+x = np.linspace(-2, 2)
+y = f(x)
+
+root = opt.newton(f, 1.5, fprime=fprime, fprime2=fprime2)
+
+plt.plot(x, y)
+plt.plot(root, 0, 'ro')
+
+ax = plt.gca()
+ax.spines['right'].set_color('none')
+ax.spines['top'].set_color('none')
+ax.xaxis.set_ticks_position('bottom')
+ax.spines['bottom'].set_position(('data', 0))
+ax.yaxis.set_ticks_position('left')
+ax.spines['left'].set_position(('data', 0))
+
+plt.savefig('cubic.pdf')
+