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Marks

Marks serve for mark-ing data points. Lilaq features a set of built-in marks, shown below. Marks can be set via the mark key for all plot types that use marks (e.g., plot.mark, scatter.mark, stem.mark).

There are two ways to specify a mark

  • Either by fetching a mark directly from lq.marks, e.g., lq.marks.star. Some marks have additional parameters that can be set here, e.g., lq.marks.star.with(n: 6).
  • Or as a string with a mark name from lq.marks. The available names are also shown in the table below.

Available marks​

The following marks are available under lq.marks.

The triangle marks ^, v, <, and > as well as p5, p6, p7, and p8 are specializations of the polygon mark which features the parameters n and angle.

The same holds for the star marks s3, s4, s5, and s6 which are specializations of the star. Aside from the parameters n and angle, this mark also features the parameter inset that determines how far the inner points are pulled to the center.

The asterisks a3, a4, a5, and a6 are specializations of the asterisk mark which is just star.with(inset: 100%). The + mark is an alias for a4.

The text mark can be used to show anything given to the body parameter, e.g., text.with(body: [Y]). Notable marks are:

  • The point mark , which is always 1pt in diameter, regardless of the mark size.
  • The general-use text mark for showing anything given to the body parameter.

Custom mark shapes​

It is easy to create a custom mark shape. A shape is just a function that receives a mark object with the fields size (a length), fill (a color), and stroke which returns the mark content.

#lq.diagram(
  lq.plot(
    (1, 2, 3, 4),
    (1, 2, 3, 4),
    stroke: none,
    mark: mark => place(
      center + horizon, text(mark.fill)[%]
    )
  )
)

There is also the special lq.marks.text marker that can be employed to quickly use any symbol (or really any content) as a marker.

Sizing​

Marks are carefully designed to match in their optical size for the same size setting. This gives a nice and homogeneous look when plotting with different marks.

The optical size of a mark is of course subjective and is influenced by a combination of the area and the dimensions of a mark.

  • The circle mark has (at least when it has no stroke) the exact radius as given through mark.size.
  • The square is a bit smaller to better match the optical size of the circle.
  • The polygons (including the diamond) with low nn are drawn with a larger circumference.
  • In addition, polygons with 3, 5, and 7 sides are shifted by a fraction to improve the optical center.
  • Stars are drawn a bit larger to compensate their lack of area.
  • The asterisk and plus marks are enlarged.