Rand Stats




CLI::Graphing::BarChart is a simple library to let you produce bar graphs on the command line. It takes special care to give you good looking output.

example graph

Currently limited to vertical bar charts. See the end of this document for future plans & contribution guidelines.


Note that the 0 x 0 point of this graph is the bottom left corner. Data and labels start from there and move outwards.

Folks using Arabic & other Right-to-Left are encouraged to make a PR to support reversed graphs.

Required Attributes

When creating a graph there are two required keys. graph_height and data.

graph_height is how tall you wish the core graph to be in lines. This does not include the additional lines for the x axis or its dividing line.

data is an array of numbers. Each is expected to be a percentage from 0 to 100. 100 create a vertical bar graph_height lines tall. 0 will create an empty bar.

Note, there will be rounding issues if your graph_height is anything other than an even multiple of 100. This is ok.

Just to set expectations, if for example, you specify a graph_height of 10 that means there are only 10 vertical elements to each bar. If one of your data points is 7 you'll end up with an empty bar because that's less than the number needed to activate the 1st element (10).

Optional Attributes

x_axis_labels This is an array of labels that must be equal in length to the number of data points. If you want some of your bars to be unlabeled then specify a space for that "label".

y_axis_labels This is an array of labels that must be equal in length to the graph_height (one label per row). Again, if you want some of the points to be unlabeled, you should use a space character.

Note that the 0 x 0 point of this graph is the bottom left. So your list of y_axis_labels will go from bottom up. This corresponds to how the data and x_axis_labels go from left to right.

space_between_columns This is a Bool which defaults to True. If you set it to False the system will not introduce a space between each column. This works fine, and may be a good choice if you have a large number of data points, but for short graphs it's almost always worse looking.


From a purely visual perspective it is not recommended that you use full words for your x_axis_labels. In order to not introduce a false sense of time compression or similar meaning, every bar gets spread out by the length of the longest label.

y_axis_labels should be fine regardless of length. They are right-aligned, and just shove the graph farther to the right.

I would not recommend generating a graph that's more than 10 characters high.

See tester.raku for examples.


This library does not support generating a legend for your graph. My advice is to use single letter x_axis_labels and then use Prettier::Table to generate a legend that explains your x axis.

use CLI::Graphing::BarChart::Vertical;

my $x_and_y_axis_graph = CLI::Graphing::BarChart::Vertical.new(
    data => [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100],
    graph_height => 10,
    x_axis_labels => <a b c d e f g h i j k>,
    y_axis_labels => <0 1 2 3 4 5 6 7 8 9>

# to get the string version of the graph

# to print the graph to Standard Out

Future + Contributing

Future Plans

This actually starts out by generating a horizontal graph and then rotates it, and adds the X axis and divider lines (see inline comments).

The plan is to add CLI::Graphing::BarChart::Horizontal to this library, by extracting the initial bit of Vertical into a common module and then building Horizontal around that.

This will happen as soon as I need it, or you need it enough to make a Pull Request.


Please do. All I ask is that you include unit tests that cover whatever changes or additions you make, and that you're fine with your contributions being distributed under the AGPL.

What kind of contributions? New Features, refactored code, more tests, etc.

For best results, please ping me on mastodon (see below) to make sure I see your PR right away.


web: masukomi
mastodon: @masukomi@connectified.com


Copyright 2023 Kay Rhodes (a.k.a. masukomi)

This library is free software; you can redistribute it and/or modify it under the AGPL 3.0 or later. See LICENSE.md for details.