# Plot a Basic 2D Histogram using Matplotlib

This post is dedicated to 2D histograms made with matplotlib, through the hist2D function.

2D histograms are useful when you need to analyse the relationship between 2 numerical variables that have a huge number of values. It is useful for avoiding the over-plotted scatterplots. The following example illustrates the importance of the bins argument. You can explicitly tell how many bins you want for the X and the Y axis. The parameters of `hist2d()` function used in the example are:

• `x, y`: input values
• `bins`: the number of bins in each dimension
• `cmap` : colormap
``````# libraries
import matplotlib.pyplot as plt
import numpy as np

# create data
x = np.random.normal(size=50000)
y = x * 3 + np.random.normal(size=50000)

# Big bins
plt.hist2d(x, y, bins=(50, 50), cmap=plt.cm.jet)
plt.show()

# Small bins
plt.hist2d(x, y, bins=(300, 300), cmap=plt.cm.jet)
plt.show()

# If you do not set the same values for X and Y, the bins won't be a square!
plt.hist2d(x, y, bins=(300, 30), cmap=plt.cm.jet)
plt.show()``````

Once you decide the bin size, it is possible to change the colour palette. Please visit the matplotlib reference page to see the available palette.

``````# Reds
plt.hist2d(x, y, bins=(50, 50), cmap=plt.cm.Reds)
plt.show()

# BuPu
plt.hist2d(x, y, bins=(50, 50), cmap=plt.cm.BuPu)
plt.show()``````

Finally, it might be useful to add a color bar on the side as a legend. You can add a color bar using `colorbar()` function.

``````plt.hist2d(x, y, bins=(50, 50), cmap=plt.cm.Greys)
plt.colorbar()
plt.show()``````

Scatterplot

Heatmap

Correlogram

Bubble

Connected Scatter

2D Density

## Contact & Edit

👋 This document is a work by Yan Holtz. Any feedback is highly encouraged. You can fill an issue on Github, drop me a message onTwitter, or send an email pasting `yan.holtz.data` with `gmail.com`.

Violin

Density

Histogram

Boxplot

Ridgeline

Scatterplot

Heatmap

Correlogram

Bubble

Connected Scatter

2D Density

Barplot

Wordcloud

Parallel

Lollipop

Circular Barplot

Treemap

Venn Diagram

Donut

Pie Chart

Dendrogram

Circular Packing

Line chart

Area chart

Stacked Area

Streamgraph

Timeseries

Map

Choropleth

Hexbin

Cartogram

Connection

Bubble

Chord Diagram

Network

Sankey

Arc Diagram

Edge Bundling

Colors

Interactivity

Animation

Cheat sheets

Caveats

3D