Polar

The polar coordinate system interprets its primary aesthetic as the angular position relative to the center, and the secondary aesthetic as the distance from the center. It is most often used for pie-charts and radar plots.

Default aesthetics

The polar coordinate system has the following default position aesthetics which will be used if no others have been provided:

  • Primary: radius (distance from center)
  • Secondary: angle (angular position)

Users can provide their own aesthetic names if needed. For example, if using x and y aesthetics:

PROJECT y, x TO polar

This maps y to radius and x to angle. This is useful when converting from a cartesian coordinate system without editing all the mappings.

Settings

  • clip: Should data be removed if it appears outside the bounds of the coordinate system. Defaults to true
  • start: The starting angle in degrees for the theta scale (-360 to 360). Controls where “0” on the angular axis begins. Defaults to 0 (12 o’clock position).
    • 0 = 12 o’clock position (top)
    • 90 = 3 o’clock position (right)
    • -90 or 270 = 9 o’clock position (left)
    • 180 = 6 o’clock position (bottom)
  • end: The ending angle in degrees for the theta scale (-360 to 360). Defaults to start + 360 (a full circle). Use this with start to create partial polar plots like gauge charts or half-circle visualizations.
  • inner: The inner radius as a proportion (0 to 1) of the outer radius. Defaults to 0 (no hole). Setting this creates a donut chart where the inner portion is empty.
    • 0 = full pie (no hole)
    • 0.3 = donut with 30% hole
    • 0.5 = donut with 50% hole

Examples

Pie chart using angle/radius aesthetics

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar

Pie chart starting at 3 o’clock

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING start => 90

Pie chart starting at 9 o’clock

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING start => -90

Half-circle gauge chart

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING start => -90, end => 90

This creates a gauge chart spanning from the 9 o’clock to 3 o’clock position (a 180° arc at the top). Note that scale expansion is applied by default so the data does not fill the whole half-circle.

Three-quarter pie chart

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING end => 270

This creates a pie chart using only 270° (three-quarters of a circle), starting from 0° (12 o’clock) and ending at 270° (9 o’clock).

Donut chart with 50% hole

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING inner => 0.5

This creates a donut chart where the inner 50% of the radius is empty, leaving a ring-shaped visualization.

Donut chart with 30% hole

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING inner => 0.3

This creates a donut chart with a smaller hole (30% of the radius).

Half-circle donut chart

VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar 
  SETTING start => -90, end => 90, inner => 0.5

This combines the start, end, and inner settings to create a half-circle donut chart (gauge style) spanning from 9 o’clock to 3 o’clock with a 50% hole.