It would be unimaginable to program a chart by hand-coding in SVG or Canvas. Fortunately, there are many different chart libraries on offer on the market. It is impossible to discuss each one of them.
Tip
We have omitted some of the products mentioned in the first edition of this book, due to a lack of competitive edge.
The chart libraries are open source, but some of them are short-lived in terms of not having a comprehensive set of basic charts, such as pie, line, and bar charts, and they look rather unfinished. Here, a handful of commercial and open source products are discussed, including all the basic charts and some with extras. Some of them still support the Flash plugin, which is an option for backwards-compatibility because SVG and canvas are not supported in older browsers. Although some of them are not free for commercial development, which is understandable, they are very affordable.
Note
See http://code.google.com/p/explorercanvas/. Many libraries use this add-on to emulate Canvas prior to IE 9.
amCharts offers a full set of charts in both 2D and 3D, with other interesting charts such as radar, bubble, candlestick, and polar. All the charts look pretty and support animations. amCharts is free for commercial use, but a credit label will be displayed in the upper-left corner of the charts. The presentation of the charts looks nice and the animations are fully customizable. The default animations, compared to Highcharts, seems slightly overdone.
Ext JS is a very popular Ajax application framework developed by Sencha, a pioneering company specializing in web application development. Ext JS 4 comes with a pure JavaScript charts library, unlike its predecessor Ext JS 3 that used the YUI 2 Flash chart library. As the market trend is moving away from Adobe Flash, Sencha responded with a home-brew charting library. Ext JS 4 covers all the basic 2D charts plus gauge and radar charts, and all the charts support animations. The license is free for open source and noncommercial usage, but a developer license is needed for commercial development. One great benefit of Ext JS charts is that integration with a comprehensive set of UI components, for example for a chart with a storage framework, makes displaying/updating both the chart and the table of data very simple to do with editors.
In Ext JS 5, the charting library has been completely restructured. Appearance is a major step forward compared to Ext JS 4: the charts look much more professionally done and on a par with other competitors. Although the Ext JS 5 chart layout, color, and animations may not be as stylish and smooth as Highcharts, it is a close call and still well-received.
Data Driven Documents (D3) is the most widely-used charting library. It was created by Bostock et al., much improved from their prior academic research work on Protovis.
Note
Bostock, Michael; Ogievetsky, Vadim; Heer, Jeffrey (October 2011), D3: Data-Driven Documents, IEEE Transactions on Visualization and Computer Graphics, IEEE Press.
The principle of D3 is pretty unique, in that it focuses on transformation in document elements. In other words, it is a decorative framework to manipulate selected elements, known as selections, through a myriad of APIs. These APIs allow users to join the selections with chart data and style them like CSS or apply specific effects. This approach enables D3 to create a wide variety of impressive charts with animations that other products cannot produce. It is an ideal tool for plotting specific scientific graphs, or graphs that require complex data visualization presentation, such as Hierarchical Edge Bundling.
The software is free for commercial use and has attracted a large user base and contribution from user communities, especially from the academic sector.
Due to its highly programmable and comparatively low-level approach, it requires a much steeper learning curve that may not appeal to less technical users or developers looking for a chart-ready solution on a production level. As for constructing 3D charts in D3, it can be a challenging task. Although D3 trumps in performance, control, and presentation, it is not for everyone.
FusionCharts is probably one of the most impressive-looking tools, and has the most comprehensive range of charts on the market. Not only does it come with a full variety of interesting 2D charts (radar, dial, map, and candlestick) available as a separate product, but it also offers fully interactive 3D charts. All the chart animations are very professionally done. FusionCharts can be run in two modes: Flash or JavaScript. Although FusionCharts comes with a higher price tag, it offers the best looking charts bundled with rotatable, animated 3D charts in column, pie, funnel, and pyramid series.
Raphaël is another free graphics library. It supports both SVG and VML for earlier browsers. It is designed like a generic graphics library, handling SVG elements, but it can be used as a charting solution. The software offers APIs to create a Canvas-like object, paper, that users can then create basic shapes or line SVG elements in. The API construct is somewhat similar to D3 in the sense that it can bind data into elements and manipulate them, but with rather more primitive methods, whereas D3 is a data-centric solution. The documentation is basic and it has a smaller user community. Like D3, it requires more effort to program a presentable chart than Highcharts and is not an ideal choice for 3D chart solutions.
