Errorbar Subsampling with Matplotlib

Introduction

In data visualization, it is sometimes useful to plot error bars to show the uncertainty or variability of the data. However, if there are many data points with similar errors, the plot can become cluttered and difficult to interpret. In such cases, we can use errorbar subsampling, which allows us to draw error bars only on a subset of data points. In this tutorial, we will use Matplotlib's errorbar function to demonstrate how to apply errorbar subsampling to our data.

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Skills Graph

Import Libraries and Generate Data

First, we need to import the necessary libraries and generate some example data to work with. In this example, we will use numpy to generate the data and matplotlib to visualize it.

import matplotlib.pyplot as plt
import numpy as np

## example data
x = np.arange(0.1, 4, 0.1)
y1 = np.exp(-1.0 * x)
y2 = np.exp(-0.5 * x)

## example variable error bar values
y1err = 0.1 + 0.1 * np.sqrt(x)
y2err = 0.1 + 0.1 * np.sqrt(x/2)

Plot All Errorbars

Next, we will plot all the error bars using the errorbar function without any subsampling. This will serve as our baseline plot.

fig, ax = plt.subplots()

ax.set_title('All Errorbars')
ax.errorbar(x, y1, yerr=y1err, label='y1')
ax.errorbar(x, y2, yerr=y2err, label='y2')

ax.legend()
plt.show()

Subsample Every 6th Errorbar

Now, let's apply errorbar subsampling to plot only every 6th error bar. We can do this by using the errorevery parameter of the errorbar function.

fig, ax = plt.subplots()

ax.set_title('Every 6th Errorbar')
ax.errorbar(x, y1, yerr=y1err, errorevery=6, label='y1')
ax.errorbar(x, y2, yerr=y2err, errorevery=6, label='y2')

ax.legend()
plt.show()

Shift Second Series by 3

In some cases, we may want to apply errorbar subsampling to different parts of our data. We can do this by specifying a tuple for the errorevery parameter. For example, let's apply errorbar subsampling to the second series, but shift it by 3 data points.

fig, ax = plt.subplots()

ax.set_title('Second Series Shifted by 3')
ax.errorbar(x, y1, yerr=y1err, label='y1')
ax.errorbar(x, y2, yerr=y2err, errorevery=(3, 6), label='y2')

ax.legend()
plt.show()

Summary

In this tutorial, we learned how to apply errorbar subsampling to our data using Matplotlib's errorbar function. By using the errorevery parameter, we can selectively plot error bars only on a subset of data points, which can help make our plots more readable and interpretable.