重采样数据

下采样会降低信号的采样率或采样大小。在本教程中，当通过拖动和缩放调整打印时，将对信号进行缩减采样。

重采样数据示例

  1. import numpy as np
  2. import matplotlib.pyplot as plt
  5. # A class that will downsample the data and recompute when zoomed.
  6. class DataDisplayDownsampler(object):
  7.     def __init__(self, xdata, ydata):
  8.         self.origYData = ydata
  9.         self.origXData = xdata
  10.         self.max_points = 50
  11.         self.delta = xdata[-1] - xdata[0]
  13.     def downsample(self, xstart, xend):
  14.         # get the points in the view range
  15.         mask = (self.origXData > xstart) & (self.origXData < xend)
  16.         # dilate the mask by one to catch the points just outside
  17.         # of the view range to not truncate the line
  18.         mask = np.convolve([1, 1], mask, mode='same').astype(bool)
  19.         # sort out how many points to drop
  20.         ratio = max(np.sum(mask) // self.max_points, 1)
  22.         # mask data
  23.         xdata = self.origXData[mask]
  24.         ydata = self.origYData[mask]
  26.         # downsample data
  27.         xdata = xdata[::ratio]
  28.         ydata = ydata[::ratio]
  30.         print("using {} of {} visible points".format(
  31.             len(ydata), np.sum(mask)))
  33.         return xdata, ydata
  35.     def update(self, ax):
  36.         # Update the line
  37.         lims = ax.viewLim
  38.         if np.abs(lims.width - self.delta) > 1e-8:
  39.             self.delta = lims.width
  40.             xstart, xend = lims.intervalx
  41.             self.line.set_data(*self.downsample(xstart, xend))
  42.             ax.figure.canvas.draw_idle()
  45. # Create a signal
  46. xdata = np.linspace(16, 365, (365-16)*4)
  47. ydata = np.sin(2*np.pi*xdata/153) + np.cos(2*np.pi*xdata/127)
  49. d = DataDisplayDownsampler(xdata, ydata)
  51. fig, ax = plt.subplots()
  53. # Hook up the line
  54. d.line, = ax.plot(xdata, ydata, 'o-')
  55. ax.set_autoscale_on(False)  # Otherwise, infinite loop
  57. # Connect for changing the view limits
  58. ax.callbacks.connect('xlim_changed', d.update)
  59. ax.set_xlim(16, 365)
  60. plt.show()

下载这个示例