Consider the scatterplot on the left hand side of this figure. A lot of dots **overlap** and make the figure hard to read. Even worse, it is impossible to determine how many data points are in each position. In this case, a solution is to cut the plotting window in several** bins,** and represent the number of data points in each bin by a color. Following the shape of the bin, this makes **Hexbin plot** or **2D histogram**.

Then, it is possible to make a **smoother** result using **Gaussian KDE** (kernel density estimate). Its representation is called a **2D density plot**, and you can add a **contour** to denote each step. See more concerning these types of graphic in the 2D density section of the python graph gallery. This plot has been inspired by this stack overflow question.

# Libraries import numpy as np import matplotlib.pyplot as plt from scipy.stats import kde # Create data: 200 points data = np.random.multivariate_normal([0, 0], [[1, 0.5], [0.5, 3]], 200) x, y = data.T # Create a figure with 6 plot areas fig, axes = plt.subplots(ncols=6, nrows=1, figsize=(21, 5)) # Everything sarts with a Scatterplot axes[0].set_title('Scatterplot') axes[0].plot(x, y, 'ko') # As you can see there is a lot of overplottin here! # Thus we can cut the plotting window in several hexbins nbins = 20 axes[1].set_title('Hexbin') axes[1].hexbin(x, y, gridsize=nbins, cmap=plt.cm.BuGn_r) # 2D Histogram axes[2].set_title('2D Histogram') axes[2].hist2d(x, y, bins=nbins, cmap=plt.cm.BuGn_r) # Evaluate a gaussian kde on a regular grid of nbins x nbins over data extents k = kde.gaussian_kde(data.T) xi, yi = np.mgrid[x.min():x.max():nbins*1j, y.min():y.max():nbins*1j] zi = k(np.vstack([xi.flatten(), yi.flatten()])) # plot a density axes[3].set_title('Calculate Gaussian KDE') axes[3].pcolormesh(xi, yi, zi.reshape(xi.shape), cmap=plt.cm.BuGn_r) # add shading axes[4].set_title('2D Density with shading') axes[4].pcolormesh(xi, yi, zi.reshape(xi.shape), shading='gouraud', cmap=plt.cm.BuGn_r) # contour axes[5].set_title('Contour') axes[5].pcolormesh(xi, yi, zi.reshape(xi.shape), shading='gouraud', cmap=plt.cm.BuGn_r) axes[5].contour(xi, yi, zi.reshape(xi.shape) )