Area Mark

Area marks are filled areas with either horizontal or vertical alignment. Area marks are often used to show change over time, using either a single area or stacked areas. Area marks can also be used to encode value ranges (min, max) or uncertainty over time.


Type-Specific Mark Properties

Property Type Description
orient String The orientation of the area mark. One of horizontal or vertical (the default). With a vertical orientation, an area mark is defined by the x, y, and (y2 or height) properties; with a horizontal orientation, the y, x and (x2 or width) properties must be specified instead.
interpolate String The interpolation method to use. One of basis, cardinal, catmull-rom, linear, monotone, natural, step, step-after, step-before. The default is linear.
tension Number The tension value in the range [0, 1] to parameterize cardinal (default 0) or catmull-rom (default 0.5) interpolation.
defined Boolean A boolean flag indicating if the current data point is defined. If false, the corresponding area segment will be omitted, creating a “break”.

General Mark Properties

Property Type Description
x Number The primary x-coordinate in pixels.
x2 Number The secondary x-coordinate in pixels.
xc Number The center x-coordinate. Incompatible with x and x2.
width Number The width of the mark in pixels, if supported.
y Number The primary y-coordinate in pixels.
y2 Number The secondary y-coordinate in pixels.
yc Number The center y-coordinate. Incompatible with y and y2.
height Number The height of the mark in pixels, if supported.
opacity Number The mark opacity from 0 (transparent) to 1 (opaque).
fill Color The fill color.
fillOpacity Number The fill opacity from 0 (transparent) to 1 (opaque).
stroke Color The stroke color.
strokeOpacity Number The stroke opacity from 0 (transparent) to 1 (opaque).
strokeWidth Number The stroke width in pixels.
strokeCap String The stroke cap for line ending style. One of butt (default), round or square.
strokeDash Number[ ] An array of [stroke, space] lengths for creating dashed or dotted lines.
strokeDashOffset Number The pixel offset at which to start the stroke dash array.
strokeJoin String The stroke line join method. One of miter (default), round or bevel.
strokeMiterLimit Number The miter limit at which to bevel a line join.
cursor String The mouse cursor used over the mark. Any valid CSS cursor type can be used.
href URL A URL to load upon mouse click. If defined, the mark acts as a hyperlink.
tooltip String The tooltip text to show upon mouse hover.

For marks that support width and height settings (including rect and area), the horizontal dimensions are determined (in order of precedence) by the x and x2 properties, the x and width properties, the x2 and width properties, or the xc and width properties. If all three of x, x2 and width are specified, the width value is ignored. The y, y2, yc and height properties are treated similarly.

For marks that do not support width or height (including path and arc) similar calculations are applied, but are only used to determine the mark’s ultimate x and y position. The width property may affect the final x position, but otherwise is not visualized.

When using multiple spatial properties along the same dimension (x and x2, or y and y2), the properties must be specified in the same encoding set; for example, all within "enter": {...} or all within "update": {...}. Dividing the properties across encoding sets can cause unexpected behavior.