Julia 2D Histogram

Introduction

A histogram is a graphical representation of the distribution of data. In Julia, creating a histogram is easy and intuitive. However, sometimes we want to visualize the distribution of two variables simultaneously. This is where the 2D histogram comes in.

A 2D histogram is a visualization where we bin the data into rectangles and color each rectangle according to the number of data points within it. This allows us to see how the two variables are related to each other and how they are distributed.

In this tutorial, we will be using the Plots package in Julia to create 2D histograms.

Getting started

First, we need to install the Plots package if we haven't already done so. We can do this by running the following command in Julia's package manager:

using Pkg
Pkg.add("Plots")

Next, let's load the Plots package:

using Plots

To demonstrate how to create a 2D histogram, let's generate some random data. In this example, we will generate 1000 data points where x and y are normally distributed:

x = randn(1000)
y = randn(1000)

Creating a 2D histogram

To create a 2D histogram with Plots, we can use the heatmap function. The heatmap function takes in two arrays, representing the x and y coordinates of the data points respectively. We can also specify the number of bins for each axis using the bins argument.

Here's an example:

heatmap(x, y, bins = 20)

This code will create a 2D histogram with 20 bins on both the x and y axes. The resulting plot should look something like this:

In this plot, the color of each rectangle represents the number of data points in that bin. The color scale is displayed on the right-hand side of the plot.

Customizing the 2D histogram

We can customize the 2D histogram in various ways by passing additional arguments to the heatmap function. Here are a few examples:

Changing the color scale

We can change the color scale by passing the c argument, which should be a string representing the name of the color map. Here's an example:

heatmap(x, y, bins = 20, c = :inferno)

This will create a 2D histogram with the 'inferno' color map:

Adding a color bar label

To add a label to the color bar, we can use the colorbar_title argument. Here's an example:

heatmap(x, y, bins = 20, c = :inferno, colorbar_title = "Count")

This will add a label to the color bar indicating that it represents the count of data points:

Changing the title and axis labels

We can change the title and axis labels of the plot by using the title, xlabel, and ylabel arguments. Here's an example:

heatmap(x, y, bins = 20, c = :inferno, title = "2D Histogram", xlabel = "X", ylabel = "Y")

This will add a title and axis labels to the plot:

Conclusion

In this tutorial, we learned how to create a 2D histogram in Julia using the Plots package. We also learned how to customize the plot by changing the color scale, adding a color bar label, and changing the title and axis labels.

With this knowledge, you can now create your own 2D histograms in Julia and explore the relationships between different variables in your data.