TP

The Gamma dataviz package now available!

There were a lot of rumors recently about the death of facts and even the death of statistics. I believe the core of the problem is that working with facts is quite tedious and the results are often not particularly exciting. Social media made it extremely easy to share your own opinions in an engaging way, but what we are missing is a similarly easy and engaging way to share facts backed by data.

This is, in essence, the motivation for The Gamma project that I've been working on recently. After several experiments, including the visualization of Olympic medalists, I'm now happy to share the first reusable component based on the work that you can try and use in your data visualization projects. If you want to get started:

The package implements a simple scripting language that anyone can use for writing simple data aggregation and data exploration scripts. The tooling for the scripting language makes it super easy to create and modify existing data analyses. Editor auto-complete offers all available operations and a spreadsheet-inspired editor lets you create scripts without writing code - yet, you still get a transparent and reproducible script as the result.

What do you get?

I experimented with a couple of ideas when working on the project and the package implements two most interesting ones:

The following gif shows the ideas in action. Given a data set that consists of a list of all the Olympic medal winners (which I used for the Olympic medalists project), we want to get a bar chart with top countries based on medals from Rio 2016:


(Open the image in a new window)

The package provides an API for running The Gamma scripts and rendering the resulting chart in a given div and it also provides an API for creating an editor that you can see in the above gif in a given div. The currently supported charting libraries are Google Charts (though it is possible to add more!) and the editor uses the Monaco editor behind the scenes.

Getting started

The easiest way to get started is to look at the developer documentation and to explore the sample web application, which is hosted live here. If you want the use The Gamma, you will need two things. First, you will need a simple REST service that provides the data for your visualizations and can execute simple queries constructed in the browser. Second, you will need to configure the JavaScript component. There is a detailed documentation for both of these on thegamma.net, but I'll briefly summarize both here.

Using the client-side component

The client-side component is available as thegamma-script on npm. In order to use it with the Monaco editor, you need to load it using require.js. Once it is loaded, all you need to do is to specify type providers that define what will be available to the person writing code. Type providers provide top-level objects such as olympics (exposing data) and chart (mapping for Google charts). The JavaScript code looks something like this:

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var services = "http://thegamma-services.azurewebsites.net/";
var libs = "/node_modules/thegamma-script/dist/libraries.json";

var providers = 
  g.providers.createProviders({ 
    "worldbank": g.providers.rest(services + "worldbank"),
    "olympics": g.providers.pivot(services + "pdata/olympics"),
    "libraries": g.providers.library(libs) });
    
var ctx = g.gamma.createContext(providers);

The g.providers API lets you define two kinds of type providers (the third one is work-in-progress and I'll add it to the documentation soon):

Once type providers are specified, you get back a context ctx which can be used to create Monaco editor, monitor errors in the code written by users and run scripts. Assuming the #demo element contains the script to run, you can execute it and display the output in #out1 element using:

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var code = document.getElementById("demo").innerText;
ctx.evaluate(code, "out1");

The context object provides the following functions:

Creating editor and reporting errors as shown in the sample web demo is similarly easy to running code. The full developer documentation explains the remaining functions of the public API.

Implementing data provider

The type provider specified using g.providers.pivot takes a URL of a data source. All you need to do to provide your own data source is to create a simple REST service (which can be written in any language) that returns metadata about your data source and can evaluate queries written using The Gamma.

The query evaluation is done on the server rather than the client. This lets you expose large data sets that would not be easy to download (the results of the query are typically smaller and can be truncated), but it means some more logic is needed on the server.

Assuming you specify http://example.com/olympics as your data source. When you create the type provider, it will first make request with ?metadata query to get information about the columns that your data set contains. The response should be a JSON record with column names as keys and types (number or string) as values:

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GET http://example.com/olympics?metadata
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{ "Games":"string", "Year":"number", "Event":"string",
  "Discipline":"string", "Athlete":"string", 
  "Sport":"string", "Gender":"string", "Team":"string",
  "Event":"string", "Medal":"string", "Gold":"number",
  "Silver":"number", "Bronze":"number" }

This is all the pivot type provider needs to generate most of the members that are available in the auto-completion list. When you finish writing code and run it, another request is issued to get the data. For the above example where we look at Rio 2016, group data by Athlete, sum number of Gold medals for each athlete, sort the results by the number of medals, take the top 3 and then get a data series with athlete and the number of medals, the query looks as follows:

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GET http://example.com/olympics?
  filter(Games eq Rio (2016))$
  groupby(by Athlete,sum Gold,key)$
  sort(Gold desc)$take(3)$series(Athlete,Gold)
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[ [ "Michael Phelps", 5 ], 
  [ "Katie Ledecky", 4 ], 
  [ "Simone Biles", 4 ] ]

As you can see, parts of the query are separated by $ and they represent the indidividual steps of the data transformation. The part series(Athlete,Gold) at the end specifies what data we want to get - here, we want to get the result as a series, which is a simple list of key value pairs, stored as nested lists.

If you want to learn more, the publishing data article explains the details of the protocol and the Olympics service shows a minimal F# example that exposed data based on a CSV file. I will be adding further examples to The Gamma repository soon, but let me know at @tomaspetricek if you have some interesting data source that you'd like to support!

Summary

When I started thinking about open and transparent visualizations more than a year ago, I did not realize how timely issue this will be. I believe that we need to build much better tools for making facts backed by data more engaging. Using a phrase from my recent talk, here is what we need!

The Gamma project is still in its early days, but the thegamma-script package that you can now use is the first step towards using data in a more fun way that encourages people to explore data on their own and produce transparent and reproducible results. Thanks to the pivot type provider and the spreadsheet-inspired editor available through The Gamma, doing that should now be a lot easier!

Published: Wednesday, 25 January 2017, 12:31 PM
Author: Tomas Petricek
Typos: Send me a pull request!
Tags: thegamma, data journalism, data science, research, visualization