skspatial.measurement.area_signed

skspatial.measurement.area_signed(points: Union[ndarray, Sequence]) → float

Return the signed area of a simple polygon given the 2D coordinates of its veritces.

The signed area is computed using the shoelace algorithm. A positive area is returned for a polygon whose vertices are given by a counter-clockwise sequence of points.

Parameters

pointsarray_like

Input 2D points.

Returns

area_signedfloat

The signed area of the polygon.

Raises

ValueError

If the points are not 2D. If there are fewer than three points.

References

https://en.wikipedia.org/wiki/Shoelace_formula https://alexkritchevsky.com/2018/08/06/oriented-area.html https://rosettacode.org/wiki/Shoelace_formula_for_polygonal_area#Python

Examples

>>> from skspatial.measurement import area_signed

>>> area_signed([[0, 0], [1, 0], [0, 1]])
0.5

>>> area_signed([[0, 0], [0, 1], [1, 0]])
-0.5

>>> area_signed([[0, 0], [0, 1], [1, 2], [2, 1], [2, 0]])
-3.0