"""

Emulate an oscilloscope. Requires the animation API introduced in

matplotlib 1.0 SVN.

"""

import numpy as np

from matplotlib.lines import Line2D

import matplotlib.pyplot as plt

import matplotlib.animation as animation

class Scope(object):

def __init__(self, ax, maxt=2, dt=0.02):

self.ax = ax

self.dt = dt

self.maxt = maxt

self.tdata = [0]

self.ydata = [0]

self.line = Line2D(self.tdata, self.ydata)

self.ax.add_line(self.line)

self.ax.set_ylim(-.1, 1.1)

self.ax.set_xlim(0, self.maxt)

def update(self, y):

lastt = self.tdata[-1]

if lastt > self.tdata[0] + self.maxt: # reset the arrays

self.tdata = [self.tdata[-1]]

self.ydata = [self.ydata[-1]]

self.ax.set_xlim(self.tdata[0], self.tdata[0] + self.maxt)

self.ax.figure.canvas.draw()

t = self.tdata[-1] + self.dt

self.tdata.append(t)

self.ydata.append(y)

self.line.set_data(self.tdata, self.ydata)

return self.line,

def emitter(p=0.03):

'return a random value with probability p, else 0'

while True:

v = np.random.rand(1)

if v > p:

yield 0.

else:

yield np.random.rand(1)

fig, ax = plt.subplots()

scope = Scope(ax)

# pass a generator in "emitter" to produce data for the update func

ani = animation.FuncAnimation(fig, scope.update, emitter, interval=10,

blit=True)

plt.show()