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2 years ago

Layers and Dual axis

You can combine different chart types with Taucharts now:


Let’s consider this in details.

As I said before, chart is a visual model of data. Quite often format of data is a sequence of data points consisting of measurements (e.g. Y1 .. Yn) made over a time interval (e.g. X).

It’s natural to desire seeing the whole picture and putting all measures on a single chart. This allows us keep an eye on particular measures in parallel as well as compare its behavior across general dynamics.

This task becomes more complex when a measures belong to significantly different scale ranges and should be plotted as different chart types.

Sample data format

Actually Taucharts has a documented workaround to handle simple cases for such data format which allows you to “unpack fields meta-data” and use simple chart types (e.g “line”) with color-coding for each measure. More advanced usage requires sophisticated customization of chart DSL.

At this stage, let me introduce a Layers plugin which simplifies such tasks in Taucharts. The plugin considers each metric provided as a composable layer which shares its X axis with the main chart. The current version allows you to make layers only with different Y axes. Categorical Y axes are not allowed – they don’t make much sense in this context.

The plugin works in 2 modes:

Well, a jsfiddle is worth a thousand words. Here some examples:

Caveat emptor with dock mode: dual axis charts is a “holy war” topic among the visualization community. There are 2 simple rules you should to consider when choosing a dual axis chart:
1) A measure belongs to significantly different ranges, so you want to keep a context of quantity for each one
2) There is a requirement to display 2 groups of measures in 2 contrasting or complementary chart types.

Please, remember that dual axis chart can accidentally hurt someone’s feelings :). Personally I always remember how Hadley Wickham reacted to a dual axis chart sample:

Hadley Wickham vs dual axis chart

Take care, Hadley’s eyes, share your feedback and have fun!