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import numpy as np
import matplotlib.pyplot as plt
# 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.ratio = 5
self.delta = xdata[-1] - xdata[0]
def downsample(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]
xdata = xdata[::self.ratio]
ydata = self.origYData[mask]
ydata = ydata[::self.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()
# Create a signal
xdata = np.linspace(16, 365, 365-16)
ydata = np.sin(2*np.pi*xdata/153) + np.cos(2*np.pi*xdata/127)
d = DataDisplayDownsampler(xdata, ydata)
fig, ax = plt.subplots()
# Hook up the line
d.line, = ax.plot(xdata, ydata, 'o-')
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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