VlChart class

A chart: a dataset, the channels every mark shares, how big it is, and the marks.

The fluent surface is a writer of specifications, not the engine. Every call writes into a specification and toSpec hands that specification over; nothing here computes a scale, a layout or a pixel. There is no path where the API computes something the engine would have computed differently, because the API computes nothing at all.

A channel said on the chart is inherited by every mark on it, so a line and the points on top of it are two marks and one set of axes rather than two charts.

A channel need not state its type — the data says. A column of numbers is a quantity, a column of ISO dates an instant, anything else a name. A field the data does not have is an error rather than a guess: errors is non-empty and the caller can say so instead of drawing an empty axis.

Since 1.0

See also VlDataset.

VlDataset data = VlDataset.create();
data.row().str("region", "North").num("sales", 120.0);
data.row().str("region", "South").num("sales", 93.0);
VlChart chart = VlChart.create(data);
chart.size(300, 200);
chart.bar().x("region").y("sales").aggregate("sum");
chart.toSpec();

VlDataset data = VlDataset.create();
data.row().str("region", "North").num("sales", 120.0);
VlChart chart = VlChart.create(data);
chart.x("region").y("sales").color("region");
chart.area().markOpacity(0.35);
chart.line();