added exam exercise 08

exam/ex08/main.py

@@ -0,0 +1,49 @@
+import numpy as np
+import matplotlib.pyplot as plt
+
+class BrownIterator(object):
+	def __init__(self, N, m):
+		self._N = N
+		self._max_m = m
+		self._i = 0
+		self._xs = None
+		self._ys = None
+	def __iter__(self):
+		self._xs = np.zeros(self._N) + 1.5
+		self._ys = np.zeros(self._N)
+		self._i = 0
+		return self
+	def __next__(self):
+		self._i += 1
+		if(self._i > self._max_m):
+			raise StopIteration()
+		if(self._i == 1):
+			return self._xs, self._ys
+
+		theta = np.random.uniform(0, np.pi * 2, self._N)
+
+		self._xs = self._xs + np.cos(theta)
+		self._ys = self._ys + np.sin(theta)
+
+		# Reflect the particles
+		self._xs[self._xs > 3] += 1.5 * (3 - self._xs[self._xs > 3])
+		self._ys[self._ys > 3] += 1.5 * (3 - self._ys[self._ys > 3])
+		self._xs[self._xs < -3] += 1.5 * (-3 - self._xs[self._xs < -3])
+		self._ys[self._ys < -3] += 1.5 * (-3 - self._ys[self._ys < -3])
+
+		return self._xs, self._ys
+
+if( __name__ == "__main__"):
+	data = np.array([i for i in BrownIterator(1000, 251)])
+	print(data)
+
+	p1, = plt.plot(data[5,0], data[5,1], "r.", label="t = 5")
+	p2, = plt.plot(data[25,0], data[25,1], "y.", label="t = 25")
+	p3, = plt.plot(data[50,0], data[50,1], "b.", label="t = 50")
+	p4, = plt.plot(data[250,0], data[250,1], "g.", label="t = 250")
+
+	plt.legend(handles=[p1, p2, p3, p4])
+	plt.show()
+
+
+