Chord PRO Released

Chord PRO is the full-featured chord visualization API, producing beautiful interactive visualizations, e.g. those featured on the front page of Reddit.

• Produce beautiful interactive Chord diagrams.
• Customize colours and font-sizes.
• Access Divided mode, enabling two sides to your diagram.
• Add images and text on hover,
• Access finer-customisations including HTML injection.
• Allows commercial use without open source requirement.
• Currently supports Python, JavaScript, and Rust, with many more to come (accepting requests).

Get it here!

Changelog:

• 05 February 2021 - Chord PRO nows supports better error messages.

• 20 January 2021 - Chord PRO now supports show(), to_html(), show_png(), to_png(), and to_pdf().

• 16 January 2021 - Chord PRO now supports disabling the custom font with load)font=False.

• 16 January 2021 - Chord PRO now supports offsetting rotation with rotate.

• 05 January 2021 - Chord PRO now supports label wrapping with wrap_labels.

• 23 December 2020 - Chord PRO now supports reverse_gradients.

• 02 December 2020 - Chord PRO now has [better support] for text customisation with the conjunction parameter.

• 21 November 2020 - Chord PRO now has better support for asymmetric chord diagrams.

• 03 November 2020 - Chord PRO now supports nodes with no relationships.

• 26 October 2020 - Chord PRO now supports Downloading to image when multiple Chord diagrams appear on the same page.

• 03 October 2020 - Chord PRO now supports visualising occurrences as well as co-occurrences.

• 29 August 2020 - Chord PRO now supports enabling a Download to image button.

• 16 August 2020 - Chord PRO now supports radius scaling and bipartite titles.

• 13 August 2020 - Chord PRO now supports Arc numbers.

• 23 July 2020 - Chord PRO now supports figure titles.

• 20 July 2020 - Chord PRO now supports asymmetric mode using symmetric=False! You can also override the verb used in the popup.

• 14 July 2020 - Chord PRO can now be enabled by entering your license key.

• 29 June 2020 - Optimisation and bug fixes to the tooltip have massively improved the interactive performance of the visualisation (Rebuild your chord diagrams to take advantage of this change).

• 22 May 2020 - Optimisation and bug fixes have massively improved the interactive performance of the visualisation (Rebuild your chord diagrams to take advantage of this change).

• 21 May 2020 - Please update to the latest version of chord. Backwards compatibility has been introduced, so from this version onwards, new versions won't break older ones!

Introduction

In a chord diagram (or radial network), entities are arranged radially as segments with their relationships visualised by arcs that connect them. The size of the segments illustrates the numerical proportions, whilst the size of the arc illustrates the significance of the relationships¹.

Chord diagrams are useful when trying to convey relationships between different entities, and they can be beautiful and eye-catching.

The Chord Package

I wanted to do a section on Chord Diagrams for my book, Data Is Beautiful.

With Python in mind, there are many libraries available for creating Chord diagrams, such as Plotly, Bokeh, and a few that are lesser-known. However, I wanted to use the implementation from d3 because it can be customised to be highly interactive and to look beautiful.

I couldn't find anything that ticked all the boxes, so I made a wrapper around d3-chord myself. It took some time to get it working, but I wanted to hide away everything behind a single constructor and method call. The tricky part was enabling multiple chord diagrams on the same page and then loading resources in a way that would support Jupyter Lab.

The primary support is for Jupyter Lab (not the older Jupyter Notebook).

Installation

Available on https://pypi.org/project/chord/ through pip:

pip install chord

Usage

Python

Python (HTML file)

Chord(matrix, names).to_html()

Jupyter Lab (Notebook)

Chord(matrix, names).show()

Defaults

Chord (free)

Chord(self,
        matrix,
        names,
        colors="d3.schemeSet1",
        opacity=0.8,
        padding=0.01,
        width=700,
        label_color="#454545",
        wrap_labels=False,
        margin=0,
        credit=False,
        font_size="16px",
        font_size_large="20px"      
    )

Chord Pro

Chord(self,
        matrix,
        names,
        colors="d3.schemeSet1",
        opacity=0.8,
        padding=0.01,
        width=700,
        label_color="#454545",
        wrap_labels=False,
        margin=0,
        credit=False,
        font_size="16px",
        font_size_large="20px",
        details=[],
        details_thumbs=[],
        thumbs_width=85,
        thumbs_margin=5,
        thumbs_font_size=14,
        popup_width=350,
        noun="instances",
        details_separator=", ",
        divide=False,
        divide_idx=0,
        divide_size=0.5,
        instances=0,
        verb="occur together in",
        symmetric=True,
        title="",
        arc_numbers=False,
        divide_left_label="",
        divide_right_label="",
        inner_radius_scale=0.39,
        outer_radius_scale=1.1,
        allow_download=False,        
    )

Examples

You can see the actual interactive examples on this page. The below examples are screenshots.

The Dataset

The focus of this section will be the demonstration of the chord package. To keep it simple, we will use synthetic data that illustrates the co-occurrences between movie genres within the same movie.

matrix = [
    [0, 5, 6, 4, 7, 4],
    [5, 0, 5, 4, 6, 5],
    [6, 5, 0, 4, 5, 5],
    [4, 4, 4, 0, 5, 5],
    [7, 6, 5, 5, 0, 4],
    [4, 5, 5, 5, 4, 0],
]

names = ["Action", "Adventure", "Comedy", "Drama", "Fantasy", "Thriller"]

Default Settings

Let's see what the Chord() defaults produce when we invoke the show() method.

Chord(matrix, names).show()

You can also save it to an HTML file.

Chord(matrix, names).to_html()

Different Colours

The defaults are nice, but what if we want different colours? You can pass in almost anything from d3-scale-chromatic, or you could pass in a list of hexadecimal colour codes.

Chord(matrix, names, colors="d3.schemeSet2").show()

Chord(matrix, names, colors=f"d3.schemeGnBu[{len(names)}]").show()

Chord(matrix, names, colors="d3.schemeSet3").show()

Chord(matrix, names, colors=f"d3.schemePuRd[{len(names)}]").show()

Chord(matrix, names, colors=f"d3.schemeYlGnBu[{len(names)}]").show()

hex_colours = ["#222222", "#333333", "#4c4c4c", "#666666", "#848484", "#9a9a9a"]

Chord(matrix, names, colors=hex_colours).show()

Label Styling

We can disable the wrapped labels, and even change the colour.

Chord(matrix, names, wrap_labels=False, label_color="#4c40bf").show()

Opacity

We can also change the default opacity of the relationships.

Chord(matrix, names, opacity=0.1).show()

Diagram Size

We can change the maximum diagram size by specifying a width.

Chord(matrix, names, width=400).show()

We can change the padding between chord segments by specifying the padding.

Chord(matrix, names, padding=0.3).show()

Data and Templates

Chord FREE package

The chord package switches to FREE mode when a username and license are not specified, or if they are both set to "free". This disables the use of all the PRO features.

This uses the Chord FREE API service hosted on the DataCrayon.com (AWS hosted) server to generate your visualisation.

Chord FREE uses the AGPL-3.0 License.

Chord PRO (full-featured) package

The chord package switches to PRO mode when a username and license are specified. This enables the use of all the PRO features.

This uses the Chord PRO API service hosted on the DataCrayon.com (AWS hosted) server to generate your visualisation.