Saturday, February 25, 2012

New feature: custom points

I'm very excited about many of the new features coming to Dygraphs. Here's one that's available today: custom points via drawPointCallback and drawHighlightPointCallback.

Dygraphs already provides a two options, drawPoints and pointSize, which will draw a small circle at every data point. Dygraphs will also draw points when hovering near a data set, and that circles size is determined by the option highlightCircleSize.

But who wants to be stuck with circles?

The drawPointCallback and drawHighlightPointCallback options both accept a function which draws the shape you want right on the canvas. As a starting point, Dygraphs now supplies a set of basic images. You can see all of them below:


The demo, which can be found here, also demonstrates drawing your own custom points, by drawing adorable little smiling and frowning faces.
More features are coming, so keep your eyes out for updates!

Wednesday, February 15, 2012

Custom lines, a new feature

A guest post by Russell Valentine.

A new series option strokePattern has been added to Dygraphs. This option allows you to define the pattern Dygraphs draws for a particular series. No longer are we limited to solid lines. It takes an even length integer array as a argument. This allows you to come up with any pattern you like for your series. This could be helpful if you have many series plots on one graph and you can not or do not want to use color alone to differentiate them. See the dygraphs per-series test page, and below for an example:

g = new Dygraph(element, data, {
    legend: ‘always’,
    strokeWidth: 2,
    colors: [‘#0000FF’],
    ‘sine wave’: {
       strokePattern: [7, 2, 2, 2]
The array defines the number of pixels that make up the drawn segments and space between them. It repeats the pattern throughout the line. The even indexes are drawn and the odd indexes are spaces. In pattern [7, 2, 2, 2] as shown in figure 2 below: seven pixels are drawn, there is a two pixel space, then two pixels are drawn then there is another two pixels space then it starts over again.

There are a few predefined patterns in Dygraphs. These are listed below, notice also when the pattern is null a solid line is used.

Dygraph.DOTTED_LINE [2, 2]
Dygraph.DASHED_LINE [7, 3]
Dygraph.DOT_DASH_LINE [7, 2, 2, 2]
null null

Dygraphs will use the strokePattern when creating the legend. If the pattern can not fit into the legend width, the pattern will be scaled to fit. This may give you unexpected results depending on the pattern you use. As an example, patterns [10, 5] and [20, 10] will look the same in the legend because they will be scaled to fit into the same width. You may need to either choose patterns that are clear in the legend or use your own legend.

The new option strokePattern is a powerful new feature for dygraphs. I hope you find it useful for your graphs.