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Terminal::Graphing::BarChart zef:masukomi last updated on 2023-02-04



Terminal::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.


Common Usage Example

use Terminal::Graphing::BarChart::Vertical;

my $x_and_y_axis_graph =
    data => [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100],
    bar_length => 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

Note that for a vertical graph the 0 x 0 point of this graph is the bottom left corner. Data and labels start from there and move outwards. BUT for a horizontal graph the 0 x 0 point is the top left corner.

``` raku

my $horizontal_graph = data => [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100], bar_length => 20, x_axis_labels => , y_axis_labels => );

to get the string version of the graph


to print the graph to Standard Out

$horizontal_graph.print(); ```

There are 3 notable restrictions in the horizontal graph

  1. x axis labels can't be longer than 1 character
  2. bar_length must be evenly divisible by the number of x axis labels.
  3. the x axis labels will be spread evenly across bar_length characters of width.

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. bar_length and data.

bar_length is how tall or wide you wish the core graph's bars to be (in characters). This does not include the additional lines for labels or the lines separating them from the graph.

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

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

Just to set expectations, if for example, you specify a bar_length of 10 that means there are only 10 vertical/horizontal 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 for the x axis. In the vertical bar chart it 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". In the horizontal bar chart it must be a number that's bar_length can be evenly divided by. In the horizontal bar chart they must also be no longer than 1 character.

For the horizontal graph I recommend just making it the same number of elements as the bar_length. That way you can precisely specify where each label appears.

y_axis_labels This is an array of labels for the y axis. In the vertical bar graph it must be equal in length to the bar_length (one label per row). Again, if you want some of the points to be unlabeled, you should use a space character. In the horizontal graph it can be less.

Note that the 0 x 0 point of the vertical graph is the bottom left. So its 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. In the horizontal bar graph it's top left so data moves from that column out.

In the Vertical bar graph you can specify 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 vertical graph that's more than 10 characters high. I would recommend making a horizontal graph that's >=20 characters wide. Otherwise they look too squished.

See vertical-graph-tester.raku and horizontal-graph-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.

Future + Contributing


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: @[email protected]


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 for details.