Script that creates heatmap with log Y and color scales

log_diagram.py

import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt

# read the data
x, y = np.loadtxt('responses.dat', unpack=True)

# change absolute timestamps to relative to start, and convert to seconds:
x = (x - x[0]) / 1000.0

# group the data points
log_bins = np.logspace(0, 4, num=100)
H, xedges, yedges = np.histogram2d(x, y, bins=(100, log_bins))

H[H < 0.1] = 0.1 

# draw the histogram
plt.rcParams['font.size'] = 10
plt.figure(figsize=(5, 2), dpi=600)
plt.pcolormesh(xedges, yedges, H.T, edgecolors='face',
               norm=mpl.colors.LogNorm(), cmap=plt.get_cmap('afmhot'))
plt.axis((xedges[0], xedges[-1], yedges[0], yedges[-1]))
plt.yscale('log')
plt.xlabel('Time, seconds')
plt.ylabel('Latency, ms')
cbar = plt.colorbar()
cbar.ax.set_ylabel('Counts')

# save the image
plt.savefig('plt-heatmap-log-palette-log.png', bbox_inches='tight')
# plt.show()