QgsKernelDensityEstimation class

Performs Kernel Density Estimation ("heatmap") calculations on a vector layer.

Reference

Public types

struct Parameters: KDE parameters.
enum KernelShape { KernelQuartic = 0, KernelTriangular, KernelUniform, KernelTriweight, KernelEpanechnikov }: Kernel shape type.
enum OutputValues { OutputRaw = 0, OutputScaled }: Output values type.
enum Result { Success, DriverError, InvalidParameters, FileCreationError, RasterIoError }: Result of operation.

Constructors, destructors, conversion operators

QgsKernelDensityEstimation(const Parameters& parameters, const QString& outputFile, const QString& outputFormat): Constructor for QgsKernelDensityEstimation.
QgsKernelDensityEstimation(const QgsKernelDensityEstimation& other) deleted: QgsKernelDensityEstimation cannot be copied.

Public functions

auto addFeature(const QgsFeature& feature) -> Result: Adds a single feature to the KDE surface.
auto finalise() -> Result: Finalises the output file.
auto operator=(const QgsKernelDensityEstimation& other) -> QgsKernelDensityEstimation& deleted: QgsKernelDensityEstimation cannot be copied.
auto prepare() -> Result: Prepares the output file for writing and setups up the surface calculation.
auto run() -> Result: Runs the KDE calculation across the whole layer at once.

Enum documentation

enum QgsKernelDensityEstimation::KernelShape

Kernel shape type.

Enumerators
KernelQuartic	Quartic kernel.
KernelTriangular	Triangular kernel.
KernelUniform	Uniform (flat) kernel.
KernelTriweight	Triweight kernel.
KernelEpanechnikov	Epanechnikov kernel.

enum QgsKernelDensityEstimation::OutputValues

Output values type.

Enumerators
OutputRaw	Output the raw KDE values.
OutputScaled	Output mathematically correct scaled values.

enum QgsKernelDensityEstimation::Result

Result of operation.

Enumerators
Success	Operation completed successfully.
DriverError	Could not open the driver for the specified format.
InvalidParameters	Input parameters were not valid.
FileCreationError	Error creating output file.
RasterIoError	Error writing to raster.

Function documentation

QgsKernelDensityEstimation::QgsKernelDensityEstimation(const Parameters& parameters, const QString& outputFile, const QString& outputFormat)

Constructor for QgsKernelDensityEstimation.

Requires a Parameters object specifying the options to use to generate the surface. The output path and file format are also required.

Result QgsKernelDensityEstimation::addFeature(const QgsFeature& feature)

Adds a single feature to the KDE surface.

prepare() must be called before adding features.

Result QgsKernelDensityEstimation::finalise()

Finalises the output file.

Must be called after adding all features via addFeature().

Result QgsKernelDensityEstimation::prepare()

Prepares the output file for writing and setups up the surface calculation.

This must be called before adding features via addFeature().

Result QgsKernelDensityEstimation::run()

Runs the KDE calculation across the whole layer at once.

Either call this method, or manually call run(), addFeature() and finalise() separately.