Chart types

Chart	Specification	Example
Bar, vertical	"type": "bar" with data	Monthly revenue
Bar, horizontal, with negative values	"orientation": "horizontal"	Quarterly change
Grouped bar, up to four series	categories and series instead of data	Budget vs. actual
Line with gaps for missing values	"type": "line", null values	Monthly trend

Each example in the repository’s examples/ folder has its rendered .svg and .html next to it. The SVG files are also the reference output of the test suite.

Several series

Replace data with categories and series. Every series needs exactly one value per category. A legend is added automatically, and the data table gets one column per series.

{
  "schemaVersion": 1,
  "type": "bar",
  "title": "Budget and actual costs",
  "categories": ["January", "February", "March"],
  "series": [
    { "name": "Budget", "values": [120, 150, 140] },
    { "name": "Actual", "values": [130, 145, null] }
  ]
}

Missing values

In a line chart, null marks an observation that does not exist. chartlet leaves a visible gap instead of drawing a line across it. In a grouped bar chart, null leaves out that bar. The data table shows these cells as “Missing”. A single-series bar chart requires a value for every category.