Wednesday, June 14, 2017

The case for pie charts

Pie charts get a lot of criticism these days. I must agree that bar charts deliver the message better because:

  • bar charts can present data for multiple categories without user interaction;
  • human eye is much better at telling differences between lengths than it is at determining differences between areas.

The charts below visualize the same data, and they all have the same size of 640x640 pixels. Decide for yourself which one does it better.

Pie chart in question - move your mouse or tap over radio buttons to change category:




Thursday, June 1, 2017

Scalable charts

Great news: charte.ca charts are now fully scalable. Content editors and users can change the size of the container - the chart will scale accordingly, preserving the original aspect ratio, without losing any functionality or quality.



Source code for this test HTML file - pay attention to the 100% width style:

<html>
  <body>
    <div>
      <embed src="example-drinking.svg"  type="image/svg+xml" style="width:100%;" />
    </div>
  <body>
<html>


To see this in action, open http://charte.ca and play with the browser window size - you will see sample charts shrinking and expanding as well.

Tuesday, May 23, 2017

Integration API: charts with live data

charte.ca integration API comes handy when you want your published chart to display up-to-date information and you do not have the luxury of logging in to the editor, tweaking the data and re-publishing the chart manually every time the data changes. Consider the following P/E ratio vs. Price to book bubble chart that we want to be updated every hour:



Tuesday, May 9, 2017

charte.ca number formatting

Users want to have the ability to tweak number formatting. No, users need this feature. Just imagine having labels like "1382323332" and "1340152688" on a diagram comparing Chinese and Indian population. Or imagine a US GDP chart with a "$20000000000000" mark on the vertical axis. Or imagine that your audience wants to see negative amounts of some specific currency: "-£349.3300".

charte.ca supports number formatting for axis marks, data labels and callouts:



Since the rules of number formatting can be complicated, we decided not to invent our own mechanism for it. We just use the standard instead: ECMAScript Internationalization API Specification. It's a long specification, but the part that we are interested in boils down to this Mozilla document. This document defines how Javascript developers can specify the locale and formatting options when converting numbers to strings. For example, an object that enables Japanese yen formatting can be instantiated as follows:

new Intl.NumberFormat('ja-JP', { style: 'currency', currency: 'JPY' });

and it can produce strings like "¥123,457". charte.ca does not provide any programming platform for chart creators, but it allows to pass the locale 'ja-JP' and the option object { style: 'currency', currency: 'JPY' } as additional parameters to the {value} keyword used in axis marks, data labels and callouts. The convention is to extend the "value" keyword with a semicolon followed by the number format specification:

NumberFormat:{locale:'<desired locale>', options:<desired options>}

For example:

{value;NumberFormat:{locale:'en', options:{useGrouping: true }}} will produce numbers with comma as a thousands separator

{value;NumberFormat:{locale:'en-US',options: style:'currency',currency:'GBP',minimumFractionDigits:4}}} will produce British pound amounts with 4 digits after decimal point.

In the example below, the callout format

{series}: {value;NumberFormat:{locale:'en', options:{useGrouping: true }}}

is specified, which makes the callout for the "0-4" age group with value 1453708 to be formatted as "0-4: 1,453,708":



Sunday, May 7, 2017

Comparative histogram charts: population by age group

Great news: charte.ca now supports comparative histograms. This kind of charts comes  handy when you want to compare two or more groups of series side-by-side. In most cases, this type of charts is used to draw a population pyramid, but it has other uses as well.

The following chart shows country population by age group, for multiple years, comparing male and female population.


This post discusses comparative histogram creation process step-by-step.

Friday, January 6, 2017

US and Canada demographics: immigration, temporary workers, refugees in 1935-2014

I was curious about the differences between American and Canadian immigration systems. After 2016 US elections, we hear a lot about those differences, but I could not find a good source with actual numbers compared. Let's do it here. As usual, here is the Google Docs spreadsheet with all relevant data. As usual, all charts below are interactive, just move your mouse over the line or the legend item.

Let's start with the simplest part - total population numbers provided by Wikipedia:


No surprises here - these countries are economically and culturally close, so population growth patterns are similar.

Let's have a look at natural population growth numbers pulled from UNDESA (UN Department of Economic and Social Affairs) and The World Bank:

Sunday, December 18, 2016

Scatter/Bubble charts and regression analysis: median income and obesity levels

Is there a correlation between median income and obesity? I have put some numbers from a few data sources (see full list in the end of the post) in a single GoogleDocs spreadsheet. I have created a new grouped bubble chart and imported the data using CSV/TSV wizard, using Region/Haplogroup column for grouping: