Contour polygons

detroit.contours()

For each threshold value, the contour generator constructs a GeoJSON MultiPolygon geometry object representing the area where the input values are greater than or equal to the threshold value. The geometry is in planar coordinates, where \((i + 0.5, j + 0.5)\) corresponds to element i + j * n in the input values array.

class detroit.contour.contours.Contours

For each threshold value, the contour generator constructs a GeoJSON MultiPolygon geometry object representing the area where the input values are greater than or equal to the threshold value. The geometry is in planar coordinates, where \((i + 0.5, j + 0.5)\) corresponds to element i + j * n in the input values array.

__call__(values: list[float]) → list[MultiPolygonGeoJSON]

Computes the contours for the given array of values, returning an array of GeoJSON MultiPolygon geometry objects.

Parameters:

values (list[float]) – Input grid values which must be an array of length \(n \times m\) where \([n, m]\) is the contour generator’s size; furthermore, each values[i + j * n] must represent the value at the position \((i, j)\).

Returns:

Geometry objects

Return type:

list[GeoJSON]

contour(values: list[float], value: float) → MultiPolygonGeoJSON

Computes a single contour

Parameters:

• values (list[float]) – Input grid values which must be an array of length \(n \times m\) where \([n, m]\) is the contour generator’s size; furthermore, each values[i + j * n] must represent the value at the position \((i, j)\).

• value (float) – Threshold value; the input values are greater than or equal to this value.

Returns:

GeoJSON MultiPolygon geometry object

Return type:

GeoJSON

set_size(size: tuple[float, float]) → Contours

Sets the size of the input values to the contour generator and returns itself.

Parameters:

size (tuple[float, float]) – Size of the input values

Returns:

Itself

Return type:

Contours

set_smooth(smooth: bool) → Contours

Sets if contour polygons are smoothed using interpolatation and returns itself.

Parameters:

smooth (bool) – Boolean value

Returns:

Itself

Return type:

Contours

set_thresholds(thresholds: Callable[[list[float], ...], float | list[float]] | list[float] | float) → Contours

Sets the threshold function to the contour generator and returns itself.

Parameters:

thresholds (Callable[[list[float], ...], float | list[float]] | list[float] | float) – Threshold function or array or constant value; default d3.threshold_sturges

Returns:

Itself

Return type:

Contours