Errorbar

Layers are declared with the DRAW clause. Read the documentation for this clause for a thorough description of how to use it.

Errorbars are used to display paired metrics, typically some interval, for a variable. It is displayed as a line between the two values, often with hinges at the ends.

Aesthetics

The following aesthetics are recognised by the errorbar layer.

Required

  • Primary axis (e.g. x): Position along the primary axis
  • Secondary axis minimum (e.g. ymin): Lower position along the secondary axis.
  • Secondary axis maximum (e.g. ymax): Upper position along the secondary axis.

Optional

  • stroke/colour: The colour of the lines in the errorbar.
  • opacity: The opacity of the colour.
  • linewidth: The width of the lines in the errorbar.
  • linetype: The dash pattern of the lines in the errorbar.

Settings

  • width: The width of the hinges in points (must be >= 0). Defaults to 10. Can be set to null to not display hinges.

Data transformation

The errorbar layer does not transform its data but passes it through unchanged.

Orientation

The orientation of errorbar layers is deduced directly from the mapping, because the interval is mapped to the secondary axis. To create a horizontal errorbar layer, you map the independent variable to y instead of x and the interval to xmin and xmax (assuming a default Cartesian coordinate system).

Examples

Create example data 
CREATE TABLE penguin_summary AS
WITH stats AS (
  SELECT species, AVG(bill_dep) AS mean
  FROM ggsql:penguins
  GROUP BY species
)
SELECT species, mean - 1.5 AS low, mean, mean + 1.5 AS high
FROM stats

Classic errorbar with point at centre.

VISUALISE species AS x FROM penguin_summary
DRAW errorbar 
  MAPPING low AS ymax, high AS ymin
DRAW point 
  MAPPING mean AS y

Dynamite plot using bars instead of points, using extra wide hinges.

VISUALISE species AS x FROM penguin_summary
DRAW errorbar 
  MAPPING low AS ymax, high AS ymin
  SETTING width => 40
DRAW bar 
  MAPPING mean AS y

The hinges can be omitted by setting null as width.

VISUALISE species AS x FROM penguin_summary
DRAW errorbar 
  MAPPING low AS ymax, high AS ymin
  SETTING width => null

A horizontal errorbar can be rendered by swapping the x and y directions.

VISUALISE species AS y FROM penguin_summary
DRAW errorbar 
  MAPPING low AS xmax, high AS xmin
DRAW point 
  MAPPING mean AS x