Density estimation¶

detroit.contour_density()¶: Constructs a new density estimator with the default settings.

class detroit.contour.density.Density¶

Constructs a new density estimator with the default settings.

__call__(data: list[T]) → list[MultiPolygonGeoJSON]¶

Estimates the density contours for the given array of data, returning an array of GeoJSON MultiPolygon geometry objects.

Parameters:: data (list[T]) – Data input
Returns:: List of GeoJSON MultiPolygon geometry objects
Return type:: list[GeoJSON]

contours(data: list[T]) → Contour¶

Return a Contour callable class that can be used to compute an arbitrary contour on the given data without needing to recompute the underlying grid. The returned contour class also exposes a Contour.max value which represents the maximum density of the grid.

Parameters:: data (list[T]) – Data input
Returns:: Callable class
Return type:: Contour

x(x: Callable[[T], float] | Callable[[T, int], float] | Callable[[T, int, list[Element]], float] | float) → Density¶

Sets the x coordinate accessor and returns itself.

Parameters:: x (Accessor[T, float] | float) – X accessor or constant value
Returns:: Itself
Return type:: Density

y(y: Callable[[T], float] | Callable[[T, int], float] | Callable[[T, int, list[Element]], float] | float) → Density¶

Sets the y coordinate accessor and returns itself.

Parameters:: y (Accessor[T, float] | float) – Y accessor or constant value
Returns:: Itself
Return type:: Density

set_weight(weight: Callable[[T], float] | Callable[[T, int], float] | Callable[[T, int, list[Element]], float] | float) → Density¶

Sets the weight accessor and returns itself.

Parameters:: x (Accessor[T, float] | float) – Weight accessor or constant value
Returns:: Itself
Return type:: Density

set_size(size: tuple[float, float]) → Density¶

Sets the size of the density estimator to the specified bounds and returns itself. The size is specified as an array [width, height] where width is the maximum x-value and height is the maximum y-value.

Parameters:: size (tuple[float, float]) – Size of the density estimator; default value [960, 500]
Returns:: Itself
Return type:: Density

set_cell_size(cell_size: float) → Density¶

Sets the size of individual cells in the underlying bin grid of the positive integer and returns itself.

Parameters:: cell_size (float) – Cell size; default value 4
Returns:: Itself
Return type:: Density

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

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

Thresholds are defined as an array of values \([x_0, x_1, ...]\). The first generated density contour corresponds to the area where the estimated density is greater than or equal to \(x_0\); the second contour corresponds to the area where the estimated density is greater than or equal to \(x_1\), and so on. Thus, there is exactly one generated MultiPolygon geometry object for each specified threshold value; the threshold value is exposed as geometry["value"]. The first value \(x_0\) should typically be greater than zero.

Parameters:: thresholds (Callable[[list[float], ...], float | list[float]] | list[float] | float) – Threshold function or array or constant value
Returns:: Itself
Return type:: Density

set_bandwidth(bandwidth: float) → Density¶

Sets the bandwidth (the standard deviation) of the Gaussian kernel and returns itself.

Parameters:: bandwidth (float) – Bandwidth value
Returns:: Itself
Return type:: Density

class detroit.contour.density.Contour(values: list[float], contours: Contours, pow4k: float, transform: Callable[[MultiPolygonGeoJSON], MultiPolygonGeoJSON])¶

Class used to compute an arbitrary contour without needing to recompute the underlying grid.

Parameters:

values (list[float]) – Computed grid values
contours (Contours) – Contours class
pow4k (float) – Computed constant value
transform (Callable[[GeoJSON], GeoJSON]) – Transform function

__call__(value: float) → MultiPolygonGeoJSON¶

Compute an arbitrary contour without needing to recompute the underlying grid.

Parameters:: value (float) – Threshold value
Returns:: GeoJSON MultiPolygon geometry object
Return type:: GeoJSON

max() → float¶

Computes the maximum density of the grid.

Returns:: Maximum density of the grid
Return type:: float