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import numpy as np
import matplotlib.pyplot as plt
from scikits.audiolab import wavread
# A class that will downsample the data and recompute when zoomed.
class DataDisplayDownsampler(object):
def __init__(self, xdata, ydata):
self.origYData = ydata
self.origXData = xdata
self.numpts = 3000
self.delta = xdata[-1] - xdata[0]
def resample(self, xstart, xend):
# Very simple downsampling that takes the points within the range
# and picks every Nth point
mask = (self.origXData > xstart) & (self.origXData < xend)
xdata = self.origXData[mask]
ratio = int(xdata.size / self.numpts) + 1
xdata = xdata[::ratio]
ydata = self.origYData[mask]
ydata = ydata[::ratio]
return xdata, ydata
def update(self, ax):
# Update the line
lims = ax.viewLim
if np.abs(lims.width - self.delta) > 1e-8:
self.delta = lims.width
xstart, xend = lims.intervalx
self.line.set_data(*self.downsample(xstart, xend))
ax.figure.canvas.draw_idle()
# Read data
data = wavread('/usr/share/sounds/purple/receive.wav')[0]
ydata = np.tile(data[:, 0], 100)
xdata = np.arange(ydata.size)
d = DataDisplayDownsampler(xdata, ydata)
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
#Hook up the line
xdata, ydata = d.downsample(xdata[0], xdata[-1])
d.line, = ax.plot(xdata, ydata)
ax.set_autoscale_on(False) # Otherwise, infinite loop
# Connect for changing the view limits
ax.callbacks.connect('xlim_changed', d.update)
plt.show()
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