My Matplotlib Cheatsheet (#2)

Previously, I wrote about some matplotlib methods I often use. In this post I will show two more.

Scatter plots with color for density

Scatter plots with many points can become very uninformative. A very easy solution is to color the points according to their local density. This can be done with the gaussian_kde from scipy.stats. Suppose that we want to make a scatter plot from xs and ys in subplot ax, then we just have to add two lines to color the points:

xy = numpy.vstack([xs, ys])
z = scipy.stats.gaussian_kde(xy)(xy)
ax.scatter(xs, ys, s=5, c=z)

Here's an example:

This is the code I used to make the figure, making use of inset_axes for a color bar:

Recycling bins for multiple histograms

When you want to plot multiple histograms in one plot, the width of the bins can be very different, which does not look so good. I recently found a simple method to fix this. The second value that the hist function returns specifies the boundaries of the bins used for the histogram. This value can be used directly in the next call to the hist function using the bins keyword. The following figure shows the result:

I used the following code to plot this figure: