Animated stripchart

This script creates a moving stripchart-style plot of a data stream. Change num_points to increase the length of the section that gets plotted. (TODO: put in a matplotlib slider widget for num_points.)

	# Monitor and plot
	from __future__ import division, print_function
	import numpy as np
	from numpy import sin, cos, random
	from scipy.constants import c,e,h,hbar,u,pi
	import matplotlib.pyplot as plt
	import matplotlib.animation as animation
	import time
	def return_values():
	time.sleep(0.2) # delay for 200 ms
	# replace the following line with a function that returns data from the labjack
	return np.random.uniform()
	# Plot and animate
	t0 = time.time()
	t = []
	t.append(time.time()-t0)
	y = []
	y.append(return_values())
	fig, ax = plt.subplots()
	t0 = time.time()
	num_points = 30 # length of trace to plot
	line, = ax.plot(t[-num_points:],y[-num_points:],lw=2)
	text_template = 'y-value = %.2g'
	text = ax.text(0.15,0.15,text_template%(y[-1]), transform=ax.transAxes, family='monospace',fontsize=20,weight='heavy')
	def animate(i):
	# add new points to time and y-value arrays
	t.append(time.time()-t0)
	y.append(return_values())
	# rescale axes to keep moving
	ax.set_xlim(t[-num_points:][0],t[-1])
	avg = np.average(y[-num_points:])
	variation = max(y[-num_points:]) - min(y[-num_points:])
	ax.set_ylim(avg - 1.2*variation/2, avg + 1.2*variation/2)
	ax.figure.canvas.draw() # this is necessary, to redraw the axes
	# refresh line and text
	line.set_xdata( t[-num_points:] )
	line.set_ydata( y[-num_points:] )
	text.set_text( text_template%(y[-1]) )
	return line, text
	def init(): #Init only required for blitting to give a clean slate.
	line.set_ydata(np.ma.array(t[-num_points:], mask=True))
	text.set_text(" ")
	return line, text
	ani = animation.FuncAnimation(fig, animate, init_func=init,
	interval=0.6, blit=False) # blit has to be False, to avoid ugly artefacts on the text
	plt.show()

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