HeatmapLayer¶

Screenshot from DuckDB Spatial example

lonboard.HeatmapLayer ¶

Bases: BaseArrowLayer

The HeatmapLayer visualizes the spatial distribution of data.

Example

From GeoPandas:

import geopandas as gpd
from lonboard import Map, HeatmapLayer

# A GeoDataFrame with Point geometries
gdf = gpd.GeoDataFrame()
layer = HeatmapLayer.from_geopandas(gdf)
m = Map(layer)

From an Arrow-compatible source like pyogrio or geoarrow-rust:

from geoarrow.rust.io import read_flatgeobuf
from lonboard import Map, HeatmapLayer

# Example: A FlatGeobuf file with Point geometries
table = read_flatgeobuf("path/to/file.fgb")
layer = HeatmapLayer(
    table,
    get_fill_color=[255, 0, 0],
)
m = Map(layer)

aggregation ¶

aggregation = Unicode(None, allow_none=True)

Defines the type of aggregation operation

Valid values are 'SUM', 'MEAN'.

Type: str, optional
Default: "SUM"

auto_highlight ¶

auto_highlight = Bool(default_value=False)

When true, the current object pointed to by the mouse pointer (when hovered over) is highlighted with highlightColor.

Requires pickable to be True.

Type: bool
Default: False

before_id ¶

before_id = Unicode(None, allow_none=True)

The identifier of a layer in the Maplibre basemap layer stack.

This deck.gl layer will be rendered just before the layer with the given identifier. You can find such an identifier by inspecting the basemap style JSON.

For example, in the Carto Positron style, if you look at the raw JSON data, each layer has an "id" property. The first layer in the basemap stack has "id": "background". So if you pass before_id="background", you won't see your deck.gl layer because it will be rendered below all layers in the Maplibre basemap.

A common choice for Carto-based styles is to use before_id="watername_ocean" so that your deck.gl layer is rendered above the core basemap elements but below all text labels.

Info

This only has an effect when the map's basemap is a MaplibreBasemap, and the map is rendering in "interleaved" mode.

debounce_timeout ¶

debounce_timeout = Int(None, allow_none=True)

Interval in milliseconds during which changes to the viewport don't trigger aggregation.

Type: int, optional
Default: 500

extensions ¶

extensions = tag(sync=True, **(widget_serialization))

A list of layer extension objects to add additional features to a layer.

get_weight ¶

get_weight = FloatAccessor(None, allow_none=True)

The weight of each object.

Type: FloatAccessor, optional
- If a number is provided, it is used as the weight for all objects.
- If an array is provided, each value in the array will be used as the weight for the object at the same row index.
Default: 1.

highlight_color ¶

highlight_color = VariableLengthTuple(
    Int(), default_value=(0, 0, 128, 128), minlen=3, maxlen=4
)

RGBA color to blend with the highlighted object (the hovered over object if auto_highlight=true). When the value is a 3 component (RGB) array, a default alpha of 255 is applied.

Type: List or Tuple of integers
Default: [0, 0, 128, 128]

intensity ¶

intensity = Float(None, allow_none=True)

Value that is multiplied with the total weight at a pixel to obtain the final weight.

Type: float, optional
Default: 1

opacity ¶

opacity = Float(1, min=0, max=1)

The opacity of the layer.

Type: float. Must range between 0 and 1.
Default: 1

pickable ¶

pickable = Bool(default_value=True)

Whether the layer responds to mouse pointer picking events.

This must be set to True for tooltips and other interactive elements to be available. This can also be used to only allow picking on specific layers within a map instance.

Note that picking has some performance overhead in rendering. To get the absolute best rendering performance with large data (at the cost of removing interactivity), set this to False.

Type: bool
Default: True

radius_pixels ¶

radius_pixels = Float(None, allow_none=True)

Radius of the circle in pixels, to which the weight of an object is distributed.

Type: float, optional
Default: 30

selected_index ¶

selected_index = Int(None, allow_none=True)

The positional index of the most-recently clicked on row of data.

You can use this to access the full row of data from a GeoDataFrame

gdf.iloc[layer.selected_index]

Setting a value here from Python will do nothing. This attribute only exists to be updated from JavaScript on a map click. Note that pickable must be True (the default) on this layer for the JavaScript onClick handler to work; if pickable is set to False, selected_index will never update.

Note that you can use observe to call a function whenever a new value is received from JavaScript. Refer here for an example.

table ¶

table = ArrowTableTrait(allowed_geometry_types={POINT})

A GeoArrow table with a Point column.

This is the fastest way to plot data from an existing GeoArrow source, such as geoarrow-rust or geoarrow-pyarrow.

If you have a GeoPandas GeoDataFrame, use from_geopandas instead.

threshold ¶

threshold = Float(None, allow_none=True, min=0, max=1)

Ratio of the fading weight to the max weight, between 0 and 1.

For example, 0.1 affects all pixels with weight under 10% of the max.

Ignored when color_domain is specified.

Type: float, optional
Default: 0.05

visible ¶

visible = Bool(default_value=True)

Whether the layer is visible.

Under most circumstances, using the visible attribute to control the visibility of layers is recommended over removing/adding the layer from the Map.layers list.

In particular, toggling the visible attribute will persist the layer on the JavaScript side, while removing/adding the layer from the Map.layers list will re-download and re-render from scratch.

Type: bool
Default: True

weights_texture_size ¶

weights_texture_size = Int(None, allow_none=True)

Specifies the size of weight texture.

Type: int, optional
Default: 2048

init ¶

__init__(
    table: ArrowStreamExportable, **kwargs: Unpack[HeatmapLayerKwargs]
) -> None

Construct a Layer from a GeoArrow table.

This accepts Arrow data from any library implementing the Arrow PyCapsule Interface, including pyarrow, arro3, DuckDB, and others.

The geometry column will be reprojected to EPSG:4326 if it is not already in that coordinate system.

Parameters:

table (ArrowStreamExportable) –

An Arrow table or stream object from a library implementing the [Arrow PyCapsule Interface]. This object must contain a column with a geometry type that has the geoarrow extension metadata.

Other Parameters:

kwargs (Unpack[BaseLayerKwargs]) –

parameters passed on to __init__

Returns:

None –

A Layer with the initialized data.

from_duckdb ¶

from_duckdb(
    sql: str | DuckDBPyRelation,
    con: DuckDBPyConnection | None = None,
    *,
    crs: str | CRS | None = None,
    **kwargs: Unpack[HeatmapLayerKwargs]
) -> Self

Construct a Layer from a duckdb-spatial query.

With DuckDB >= 1.5, the CRS of a GEOMETRY column is read automatically from the column type (e.g. GEOMETRY('EPSG:3857')) and the data is reprojected to EPSG:4326 as needed.

The crs keyword parameter is deprecated for such input and is only needed when the data cannot describe its own CRS: WKB_BLOB or 2D columns (POINT_2D, LINESTRING_2D, POLYGON_2D, BOX_2D), DuckDB older than 1.5, or a GEOMETRY column without a CRS encoded. In those cases, the user must ensure that data has been reprojected to EPSG:4326 or pass the existing CRS of the data in the crs keyword parameter.

Parameters:

sql (str | DuckDBPyRelation) –

The SQL input to visualize. This can either be a string containing a SQL query or the output of the duckdb sql function.
con (DuckDBPyConnection | None, default: None ) –

The current DuckDB connection. This is required when passing a str to the sql parameter.

Other Parameters:

crs (str | CRS | None) –

The CRS of the input data, for input that cannot describe its own CRS (see above). This can either be a string passed to pyproj.CRS.from_user_input or a pyproj.CRS object. Errors if it conflicts with the CRS encoded in a DuckDB >= 1.5 GEOMETRY column. Defaults to None.
kwargs (Unpack[BaseLayerKwargs]) –

parameters passed on to __init__

Returns:

Self –

A Layer with the initialized data.

from_geopandas ¶

from_geopandas(
    gdf: GeoDataFrame,
    *,
    auto_downcast: bool = True,
    **kwargs: Unpack[HeatmapLayerKwargs]
) -> Self

Construct a Layer from a geopandas GeoDataFrame.

The GeoDataFrame will be reprojected to EPSG:4326 if it is not already in that coordinate system.

Parameters:

gdf (GeoDataFrame) –

The GeoDataFrame to set on the layer.

Other Parameters:

auto_downcast (bool) –

If True, automatically downcast to smaller-size data types if possible without loss of precision. This calls pandas.DataFrame.convert_dtypes and pandas.to_numeric under the hood.
kwargs (Unpack[BaseLayerKwargs]) –

parameters passed on to __init__

Returns:

Self –

A Layer with the initialized data.

HeatmapLayer¶

lonboard.HeatmapLayer ¶

aggregation ¶

auto_highlight ¶

before_id ¶

debounce_timeout ¶

extensions ¶

get_weight ¶

highlight_color ¶

intensity ¶

opacity ¶

pickable ¶

radius_pixels ¶

selected_index ¶

table ¶

threshold ¶

visible ¶

weights_texture_size ¶

__init__ ¶

from_duckdb ¶

from_geopandas ¶

init ¶