libpysal.graph.Graph

class libpysal.graph.Graph(adjacency, transformation='O', is_sorted=False)

Graph class encoding spatial weights matrices

The Graph is currently experimental and its API is incomplete and unstable.

__init__(adjacency, transformation='O', is_sorted=False)

Weights base class based on adjacency list

It is recommenced to use one of the from_* or build_* constructors rather than invoking __init__ directly.

Each observation needs to be present in the focal, at least as a self-loop with a weight 0.

Parameters:

adjacencypandas.Series

A MultiIndexed pandas.Series with "focal" and "neigbor" levels encoding adjacency, and values encoding weights. By convention, isolates are encoded as self-loops with a weight 0.

transformationstr, default “O”

weights transformation used to produce the table.

• O – Original

• B – Binary

• R – Row-standardization (global sum \(=n\))

• D – Double-standardization (global sum \(=1\))

• V – Variance stabilizing

• C – Custom

is_sortedbool, default False

adjacency capturing the graph needs to be canonically sorted to initialize the class. The MultiIndex needs to be ordered i–>j on both focal and neighbor levels according to the order of ids in the original data from which the Graph is created. Sorting is performed by default based on the order of unique values in the focal level. Set is_sorted=True to skip this step if the adjacency is already canonically sorted.

Methods

__init__(adjacency[, transformation, is_sorted])	Weights base class based on adjacency list
aggregate(func)	Aggregate weights within a neighbor set
apply(y, func, **kwargs)	Apply a reduction across the neighbor sets
assign_self_weight([weight])	Assign values to edges representing self-weight.
asymmetry([intrinsic])	Asymmetry check.
build_block_contiguity(regimes)	Generate Graph from block contiguity (regime neighbors)
build_contiguity(geometry[, rook, ...])	Generate Graph from geometry based on contiguity
build_distance_band(data, threshold[, ...])	Generate Graph from geometry based on a distance band
build_fuzzy_contiguity(geometry[, ...])	Generate Graph from fuzzy contiguity
build_kernel(data[, kernel, k, bandwidth, ...])	Generate Graph from geometry data based on a kernel function
build_knn(data, k[, metric, p, coincident])	Generate Graph from geometry data based on k-nearest neighbors search
build_spatial_matches(data, k[, metric, ...])	Match locations in one dataset to at least n_matches locations in another (possibly identical) dataset by minimizing the total distance between matched locations.
build_triangulation(data[, method, ...])	Generate Graph from geometry based on triangulation
copy([deep])	Make a copy of this Graph's adjacency table and transformation
difference(right)	Provide the set difference between the graph on the left and the graph on the right.
eliminate_zeros()	Remove graph edges with zero weight
equals(right)	Check that two graphs are identical.
explore(gdf[, focal, nodes, color, ...])	Plot graph as an interactive Folium Map
from_W(w)	Create an experimental Graph from libpysal.weights.W object
from_adjacency(adjacency[, focal_col, ...])	Create a Graph from a pandas DataFrame formatted as an adjacency list
from_arrays(focal_ids, neighbor_ids, weight, ...)	Generate Graph from arrays of indices and weights of the same length
from_dicts(neighbors[, weights])	Generate Graph from dictionaries of neighbors and weights
from_sparse(sparse[, ids])	Convert a scipy.sparse array to a PySAL Graph object.
from_weights_dict(weights_dict)	Generate Graph from a dict of dicts
higher_order([k, shortest_path, diagonal, ...])	Contiguity weights object of order \(k\).
intersection(right)	Returns a binary Graph, that includes only those neighbor pairs that exist in both left and right.
intersects(right)	Returns True if left and right share at least one link, irrespective of weights value.
isomorphic(right)	Check that two graphs are isomorphic.
issubgraph(right)	Return True if every link in the left Graph also occurs in the right Graph.
lag(y)	Spatial lag operator
plot(gdf[, focal, nodes, color, edge_kws, ...])	Plot edges and nodes of the Graph
subgraph(ids)	Returns a subset of Graph containing only nodes specified in ids
symmetric_difference(right)	Filter out links that are in both left and right Graph objects.
to_W()	Convert Graph to a libpysal.weights.W object
to_networkx()	Convert Graph to a networkx graph.
to_parquet(path, **kwargs)	Save Graph to a Apache Parquet
transform(transformation)	Transformation of weights
union(right)	Provide the union of two Graph objects, collecing all links that are in either graph.

Attributes

adjacency	Return a copy of the adjacency list
cardinalities	Number of neighbors for each observation
component_labels	Get component labels per observation
isolates	Index of observations with no neighbors
n	Number of observations.
n_components	Get a number of connected components
n_edges	Number of observations.
n_nodes	Number of observations.
neighbors	Get neighbors dictionary
nonzero	Number of nonzero weights.
pct_nonzero	Percentage of nonzero weights.
sparse	Return a scipy.sparse array (COO)
unique_ids	Unique IDs used in the Graph
weights	Get weights dictionary

property adjacency

Return a copy of the adjacency list

Returns:

pandas.Series

Underlying adjacency list

aggregate(func)

Aggregate weights within a neighbor set

Apply a custom aggregation function to a group of weights of the same focal geometry.

Parameters:

funccallable()

A callable accepted by pandas groupby.agg method

Returns:

pd.Series

Aggregated weights

apply(y, func, **kwargs)

Apply a reduction across the neighbor sets

Applies func over groups of y defined by neighbors for each focal.

Parameters:

yarray_like

array of values to be grouped. Can be 1-D or 2-D and will be coerced to a pandas object

funcfunction, str, list, dict or None

Function to use for aggregating the data passed to pandas GroupBy.apply.

Returns:

Series | DataFrame

pandas object indexed by unique_ids

assign_self_weight(weight=1)

Assign values to edges representing self-weight.

The value for each focal == neighbor location in the graph is set to weight.

Parameters:

weightfloat | array_like

Defines the value(s) to which the weight representing the relationship with itself should be set. If a constant is passed then each self-weight will get this value (default is 1). An array of length Graph.n can be passed to set explicit values to each self-weight (assumed to be in the same order as original data).

Returns:

Graph

A new Graph with added self-weights.

asymmetry(intrinsic=True)

Asymmetry check.

Parameters:

intrinsicbool, optional

Default is True. Intrinsic symmetry is defined as:

\[w_{i,j} == w_{j,i}\]

If intrinsic is False symmetry is defined as:

\[i \in N_j \ \& \ j \in N_i\]

where \(N_j\) is the set of neighbors for \(j\), e.g., True requires equality of the weight to consider two links equal, False requires only a presence of a link with a non-zero weight.

Returns:

pandas.Series

A Series of (i,j) pairs of asymmetries sorted ascending by the focal observation (index value), where i is the focal and j is the neighbor. An empty Series is returned if no asymmetries are found.

classmethod build_block_contiguity(regimes)

Generate Graph from block contiguity (regime neighbors)

Block contiguity structures are relevant when defining neighbor relations based on membership in a regime. For example, all counties belonging to the same state could be defined as neighbors, in an analysis of all counties in the US.

Parameters:

regimeslist-like

list-like of regimes. If pandas.Series, its index is used to encode Graph. Otherwise a default RangeIndex is used.

Returns:

Graph

libpysal.graph.Graph encoding block contiguity

classmethod build_contiguity(geometry, rook=True, by_perimeter=False, strict=False)

Generate Graph from geometry based on contiguity

Contiguity builder assumes that all geometries are forming a coverage, i.e. a non-overlapping mesh and neighbouring geometries share only points or segments of their exterior boundaries. In practice, build_contiguity is capable of creating a Graph of partially overlapping geometries when strict=False, by_perimeter=False, but that would not strictly follow the definition of queen or rook contiguity.

Parameters:

geometryarray_like of shapely.Geometry objects

Could be geopandas.GeoSeries or geopandas.GeoDataFrame, in which case the resulting Graph is indexed by the original index. If an array of shapely.Geometry objects is passed, Graph will assume a RangeIndex.

rookbool, optional

Contiguity method. If True, two geometries are considered neighbours if they share at least one edge. If False, two geometries are considered neighbours if they share at least one vertex. By default True

by_perimeterbool, optional

If True, weight represents the length of the shared boundary between adjacent units, by default False. For row-standardized version of perimeter weights, use Graph.build_contiguity(gdf, by_perimeter=True).transform("r").

strictbool, optional

Use the strict topological method. If False, the contiguity is determined based on shared coordinates or coordinate sequences representing edges. This assumes geometry coverage that is topologically correct. This method is faster but can miss some relations. If True, the contiguity is determined based on geometric relations that do not require precise topology. This method is slower but will result in correct contiguity even if the topology of geometries is not optimal. By default False.

Returns:

Graph

libpysal.graph.Graph encoding contiguity weights

classmethod build_distance_band(data, threshold, binary=True, alpha=-1.0, kernel=None, bandwidth=None)

Generate Graph from geometry based on a distance band

Parameters:

datanumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame

geometries containing locations to compute the delaunay triangulation. If a geopandas object with Point geometry is provided, the .geometry attribute is used. If a numpy.ndarray with shapely geometry is used, then the coordinates are extracted and used. If a numpy.ndarray of a shape (2,n) is used, it is assumed to contain x, y coordinates.

thresholdfloat

distance band

binarybool, optional

If True \(w_{ij}=1\) if \(d_{i,j}<=threshold\), otherwise \(w_{i,j}=0\). If False \(wij=dij^{alpha}\), by default True.

alphafloat, optional

distance decay parameter for weight (default -1.0) if alpha is positive the weights will not decline with distance. Ignored if binary=True or kernel is not None.

kernelstr, optional

kernel function to use in order to weight the output graph. See Graph.build_kernel() for details. Ignored if binary=True.

bandwidthfloat (default: None)

distance to use in the kernel computation. Should be on the same scale as the input coordinates. Ignored if binary=True or kernel=None.

Returns:

Graph

libpysal.graph.Graph encoding distance band weights

classmethod build_fuzzy_contiguity(geometry, tolerance=None, buffer=None, predicate='intersects')

Generate Graph from fuzzy contiguity

Fuzzy contiguity relaxes the notion of contiguity neighbors for the case of geometry collections that violate the condition of planar enforcement. It handles three types of conditions present in such collections that would result in missing links when using the regular contiguity methods.

The first are edges for nearby polygons that should be shared, but are digitized separately for the individual polygons and the resulting edges do not coincide, but instead the edges intersect. This case can also be covered by build_contiguty with the strict=False parameter.

The second case is similar to the first, only the resultant edges do not intersect but are “close”. The optional buffering of geometry then closes the gaps between the polygons and a resulting intersection is encoded as a link.

The final case arises when one polygon is “inside” a second polygon but is not encoded to represent a hole in the containing polygon.

It is also possible to create a contiguity based on a custom spatial predicate.

Parameters:

geomsarray_like of shapely.Geometry objects

Could be geopandas.GeoSeries or geopandas.GeoDataFrame, in which case the resulting Graph is indexed by the original index. If an array of shapely.Geometry objects is passed, Graph will assume a RangeIndex.

tolerancefloat, optional

The percentage of the length of the minimum side of the bounding rectangle for the geoms to use in determining the buffering distance. Either tolerance or buffer may be specified but not both. By default None.

bufferfloat, optional

Exact buffering distance in the units of geoms.crs. Either tolerance or buffer may be specified but not both. By default None.

predicatestr, optional

The predicate to use for determination of neighbors. Default is ‘intersects’. If None is passed, neighbours are determined based on the intersection of bounding boxes. See the documentation of geopandas.GeoSeries.sindex.query for allowed predicates.

Returns:

Graph

libpysal.graph.Graph encoding fuzzy contiguity

classmethod build_kernel(data, kernel='gaussian', k=None, bandwidth=None, metric='euclidean', p=2, coincident='raise')

Generate Graph from geometry data based on a kernel function

Parameters:

datanumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame

geometries over which to compute a kernel. If a geopandas object with Point geoemtry is provided, the .geometry attribute is used. If a numpy.ndarray with shapely geoemtry is used, then the coordinates are extracted and used. If a numpy.ndarray of a shape (2,n) is used, it is assumed to contain x, y coordinates. If metric=”precomputed”, data is assumed to contain a precomputed distance metric.

kernelstr or callable() (default: ‘gaussian’)

kernel function to apply over the distance matrix computed by metric. The following kernels are supported:

• "triangular":

• "parabolic":

• "gaussian":

• "bisquare":

• "cosine":

• 'boxcar'/discrete: all distances less than bandwidth are 1, and all other distances are 0

• "identity"/None : do nothing, weight similarity based on raw distance

• callable : a user-defined function that takes the distance vector and the bandwidth and returns the kernel: kernel(distances, bandwidth)

kint (default: None)

number of nearest neighbors used to truncate the kernel. This is assumed to be constant across samples. If None, no truncation is conduted.

bandwidthfloat (default: None)

distance to use in the kernel computation. Should be on the same scale as the input coordinates.

metricstr or callable() (default: ‘euclidean’)

distance function to apply over the input coordinates. Supported options depend on whether or not scikit-learn is installed. If so, then any distance function supported by scikit-learn is supported here. Otherwise, only euclidean, minkowski, and manhattan/cityblock distances are admitted.

pint (default: 2)

parameter for minkowski metric, ignored if metric != “minkowski”.

coincident: str, optional (default “raise”)

Method for handling coincident points when k is not None. Options are 'raise' (raising an exception when coincident points are present), 'jitter' (randomly displace coincident points to produce uniqueness), & 'clique' (induce fully-connected sub cliques for coincident points).

Returns:

Graph

libpysal.graph.Graph encoding kernel weights

classmethod build_knn(data, k, metric='euclidean', p=2, coincident='raise')

Generate Graph from geometry data based on k-nearest neighbors search

Parameters:

datanumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame

geometries over which to compute a kernel. If a geopandas object with Point geoemtry is provided, the .geometry attribute is used. If a numpy.ndarray with shapely geoemtry is used, then the coordinates are extracted and used. If a numpy.ndarray of a shape (2,n) is used, it is assumed to contain x, y coordinates.

kint

number of nearest neighbors.

metricstr or callable() (default: ‘euclidean’)

distance function to apply over the input coordinates. Supported options depend on whether or not scikit-learn is installed. If so, then any distance function supported by scikit-learn is supported here. Otherwise, only euclidean, minkowski, and manhattan/cityblock distances are admitted.

pint (default: 2)

parameter for minkowski metric, ignored if metric != “minkowski”.

coincident: str, optional (default “raise”)

Method for handling coincident points. Options include 'raise' (raising an exception when coincident points are present), 'jitter' (randomly displace coincident points to produce uniqueness), & 'clique' (induce fully-connected sub cliques for coincident points).

Returns:

Graph

libpysal.graph.Graph encoding KNN weights

classmethod build_spatial_matches(data, k, metric='euclidean', solver=None, allow_partial_match=False, **metric_kwargs)

Match locations in one dataset to at least n_matches locations in another (possibly identical) dataset by minimizing the total distance between matched locations.

Letting \(d_{ij}\) be

\[ \begin{align}\begin{aligned}\text{minimize} \sum_i^n \sum_j^n d_{ij}m_{ij}\\\text{subject to} \sum_j^n m_{ij} >= k \forall i\\ m_{ij} \in {0,1} \forall ij\end{aligned}\end{align} \]

Parameters:

xnumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame

geometries that need matches. If a geopandas.Geo* object is provided, the .geometry attribute is used. If a numpy.ndarray with a geometry dtype is used, then the coordinates are extracted and used.

ynumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame (default: None)

geometries that are used as a source for matching. If a geopandas object is provided, the .geometry attribute is used. If a numpy.ndarray with a geometry dtype is used, then the coordinates are extracted and used. If none, matches are made within x.

n_matchesint (default: None)

number of matches

metricstr or callable() (default: ‘euclidean’)

distance function to apply over the input coordinates. Supported options depend on whether or not scikit-learn is installed. If so, then any distance function supported by scikit-learn is supported here. Otherwise, only euclidean, minkowski, and manhattan/cityblock distances are admitted.

solversolver from pulp (default: None)

a solver defined by the pulp optimization library. If no solver is provided, pulp’s default solver will be used. This is generally pulp.COIN(), but this may vary depending on your configuration.

return_mipbool (default: False)

whether or not to return the instance of the pulp.LpProblem. By default, the problem is not returned to the user.

allow_partial_matchbool (default: False)

whether to allow for partial matching. A partial match may have a weight between zero and one, while a “full” match (by default) must have a weight of either zero or one. A partial matching may have a shorter total distance, but will result in a weighted graph.

classmethod build_triangulation(data, method='delaunay', bandwidth=inf, kernel='boxcar', clip='bounding_box', rook=True, coincident='raise')

Generate Graph from geometry based on triangulation

Parameters:

datanumpy.ndarray, geopandas.GeoSeries, geopandas.GeoDataFrame

geometries containing locations to compute the delaunay triangulation. If a geopandas object with Point geoemtry is provided, the .geometry attribute is used. If a numpy.ndarray with shapely geoemtry is used, then the coordinates are extracted and used. If a numpy.ndarray of a shape (2,n) is used, it is assumed to contain x, y coordinates.

methodstr, (default “delaunay”)

method of extracting the weights from triangulation. Supports:

• "delaunay"

• "gabriel"

• "relative_neighborhood"

• "voronoi"

bandwidthfloat, optional

distance to use in the kernel computation. Should be on the same scale as the input coordinates, by default numpy.inf

kernelstr, optional

kernel function to use in order to weight the output graph. See Graph.build_kernel() for details. By default “boxcar”

clipstr (default: ‘bbox’)

Clipping method when method="voronoi". Ignored otherwise. Default is 'bounding_box'. Options are as follows.

• None – No clip is applied. Voronoi cells may be arbitrarily

larger that the source map. Note that this may lead to cells that are many orders of magnitude larger in extent than the original map. Not recommended. * 'bounding_box' – Clip the voronoi cells to the bounding box of the input points. * 'convex_hull' – Clip the voronoi cells to the convex hull of the input points. * 'alpha_shape' – Clip the voronoi cells to the tightest hull that contains all points (e.g. the smallest alpha shape, using libpysal.cg.alpha_shape_auto()). * shapely.Polygon – Clip to an arbitrary Polygon.

rookbool, optional

Contiguity method when method="voronoi". Ignored otherwise. If True, two geometries are considered neighbours if they share at least one edge. If False, two geometries are considered neighbours if they share at least one vertex. By default True

coincident: str, optional (default “raise”)

Method for handling coincident points. Options include 'raise' (raising an exception when coincident points are present), 'jitter' (randomly displace coincident points to produce uniqueness), & 'clique' (induce fully-connected sub cliques for coincident points).

Returns:

Graph

libpysal.graph.Graph encoding triangulation weights

property cardinalities

Number of neighbors for each observation

Returns:

pandas.Series

Series with a number of neighbors per each observation

property component_labels

Get component labels per observation

Returns:

numpy.array

Array of component labels

copy(deep=True)

Make a copy of this Graph’s adjacency table and transformation

Parameters:

deepbool, optional

Make a deep copy of the adjacency table, by default True

Returns:

Graph

libpysal.graph.Graph as a copy of the original

eliminate_zeros()

Remove graph edges with zero weight

Eliminates edges with weight == 0 that do not encode an isolate. This is useful to clean-up edges that will make no effect in operations like lag().

Returns:

Graph

subset of Graph with zero-weight edges eliminated

explore(gdf, focal=None, nodes=True, color='black', edge_kws=None, node_kws=None, focal_kws=None, m=None, **kwargs)

Plot graph as an interactive Folium Map

Parameters:

gdfgeopandas.GeoDataFrame

geodataframe used to instantiate to Graph

focallist, optional

subset of focal observations to plot in the map, by default None. If none, all relationships are plotted

nodesbool, optional

whether to display observations as nodes in the map, by default True

colorstr, optional

color applied to nodes and edges, by default “black”

edge_kwsdict, optional

additional keyword arguments passed to geopandas explore function when plotting edges, by default None

node_kwsdict, optional

additional keyword arguments passed to geopandas explore function when plotting nodes, by default None

focal_kwsdict, optional

additional keyword arguments passed to geopandas explore function when plotting focal observations, by default None. Only applicable when passing a subset of nodes with the focal argument

mFolilum.Map, optional

folium map objecto to plot on top of, by default None

**kwargsdict, optional

additional keyword arguments are passed directly to geopandas.explore, when m=None by default None

Returns:

folium.Map

folium map

classmethod from_W(w)

Create an experimental Graph from libpysal.weights.W object

Parameters:

wlibpysal.weights.W

Returns:

Graph

libpysal.graph.Graph from W

classmethod from_adjacency(adjacency, focal_col='focal', neighbor_col='neighbor', weight_col='weight')

Create a Graph from a pandas DataFrame formatted as an adjacency list

Parameters:

adjacencypandas.DataFrame

a dataframe formatted as an ajacency list. Should have columns “focal”, “neighbor”, and “weight”, or columns that can be mapped to these (e.g. origin, destination, cost)

focalstr, optional

name of column holding focal/origin index, by default ‘focal’

neighborstr, optional

name of column holding neighbor/destination index, by default ‘neighbor’

weightstr, optional

name of column holding weight values, by default ‘weight’

Returns:

Graph

libpysal.graph.Graph

classmethod from_arrays(focal_ids, neighbor_ids, weight, **kwargs)

Generate Graph from arrays of indices and weights of the same length

The arrays needs to be sorted in a way ensuring that focal_ids.unique() is equal to the index of original observations from which the Graph is being built

Parameters:

focal_indexarray_like

focal indices

neighbor_indexarray_like

neighbor indices

weightarray_like

weights

**kwargs

keyword arguments passed to the class constructor

Returns:

Graph

libpysal.graph.Graph based on arrays

classmethod from_dicts(neighbors, weights=None)

Generate Graph from dictionaries of neighbors and weights

Parameters:

neighborsdict

dictionary of neighbors with the {focal: [neighbor1, neighbor2]} structure

weightsdict, optional

dictionary of neighbors with the {focal: [weight1, weight2]} structure. If None, assumes binary weights.

Returns:

Graph

libpysal.graph.Graph based on dictionaries

classmethod from_sparse(sparse, ids=None)

Convert a scipy.sparse array to a PySAL Graph object.

Parameters:

sparsescipy.sparse array

sparse representation of a graph

idslist-like, default None

list-like of ids for geometries that is mappable to positions from sparse. If None, the positions are used as labels.

Returns:

Graph

libpysal.graph.Graph based on sparse

classmethod from_weights_dict(weights_dict)

Generate Graph from a dict of dicts

Parameters:

weights_dictdictionary of dictionaries

weights dictionary with the {focal: {neighbor: weight}} structure.

Returns:

Graph

libpysal.graph.Graph based on weights dictionary of dictionaries

higher_order(k=2, shortest_path=True, diagonal=False, lower_order=False)

Contiguity weights object of order \(k\).

Proper higher order neighbors are returned such that \(i\) and \(j\) are \(k\)-order neighbors if the shortest path from \(i-j\) is of length \(k\).

Parameters:

kint, optional

Order of contiguity. By default 2.

shortest_pathbool, optional

If True, \(i,j\) and \(k\)-order neighbors if the shortest path for \(i,j\) is \(k\). If False, \(i,j\) are k-order neighbors if there is a path from \(i,j\) of length \(k\). By default True.

diagonalbool, optional

If True, keep \(k\)-order (\(i,j\)) joins when \(i==j\). If False, remove \(k\)-order (\(i,j\)) joins when \(i==j\). By default False.

lower_orderbool, optional

If True, include lower order contiguities. If False return only weights of order \(k\). By default False.

Returns:

Graph

higher order weights

property isolates

Index of observations with no neighbors

Isolates are encoded as a self-loop with the weight == 0 in the adjacency table.

Returns:

pandas.Index

Index with a subset of observations that do not have any neighbor

lag(y)

Spatial lag operator

If weights are row standardized, returns the mean of each observation’s neighbors; if not, returns the weighted sum of each observation’s neighbors.

Parameters:

yarray_like

array-like (N,) shape where N is equal to number of observations in self.

Returns:

numpy.ndarray

array of numeric values for the spatial lag

property n

Number of observations.

property n_components

Get a number of connected components

Returns:

int

number of components

property n_edges

Number of observations.

property n_nodes

Number of observations.

property neighbors

Get neighbors dictionary

Returns:

dict

dict of tuples representing neighbors

Notes

It is recommended to work directly with Graph.adjacency() rather than using the Graph.neighbors().

property nonzero

Number of nonzero weights.

property pct_nonzero

Percentage of nonzero weights.

plot(gdf, focal=None, nodes=True, color='k', edge_kws=None, node_kws=None, focal_kws=None, ax=None, figsize=None, limit_extent=False)

Plot edges and nodes of the Graph

Creates a maptlotlib plot based on the topology stored in the Graph and spatial location defined in gdf.

Parameters:

gdfgeopandas.GeoDataFrame

Geometries indexed using the same index as Graph. Geometry types other than points are converted to centroids encoding start and end point of Graph edges.

focalhashable | array_like[hashable] | None, optional

ID or an array-like of IDs of focal geometries whose weights shall be plotted. If None, all weights from all focal geometries are plotted. By default None

nodesbool, optional

Plot nodes as points, by default True

colorstr, optional

The color of all objects, by default “k”

edge_kwsdict, optional

Keyword arguments dictionary to send to LineCollection, which provides fine-grained control over the aesthetics of the edges in the plot. By default None

node_kwsdict, optional

Keyword arguments dictionary to send to ax.scatter, which provides fine-grained control over the aesthetics of the nodes in the plot. By default None

focal_kwsdict, optional

Keyword arguments dictionary to send to ax.scatter, which provides fine-grained control over the aesthetics of the focal nodes in the plot on top of generic node_kws. Values of node_kws are updated from focal_kws. Ignored if focal=None. By default None

axmatplotlib.axes.Axes, optional

Axis on which to plot the weights. If None, a new figure and axis are created. By default None

figsizetuple, optional

figsize used to create a new axis. By default None

limit_extentbool, optional

limit the extent of the axis to the extent of the plotted graph, by default False

Returns:

matplotlib.axes.Axes

Axis with the resulting plot

Notes

If you’d like to overlay the actual geometries from the geopandas.GeoDataFrame, create an axis by plotting the GeoDataFrame and plot the Graph on top.

ax = gdf.plot() gdf_graph.plot(gdf, ax=ax)

property sparse

Return a scipy.sparse array (COO)

Returns:

scipy.sparse.COO

sparse representation of the adjacency

subgraph(ids)

Returns a subset of Graph containing only nodes specified in ids

The resulting subgraph contains only the nodes in ids and the edges between them or zero-weight self-loops in case of isolates.

The order of ids reflects a new canonical order of the resulting subgraph. This means ids should be equal to the index of the DataFrame containing data linked to the graph to ensure alignment of sparse representation of subgraph.

Parameters:

idsarray_like

An array of node IDs to be retained

Returns:

Graph

A new Graph that is a subset of the original

Notes

Unlike the implementation in networkx, this creates a copy since Graphs in libpysal are immutable.

to_W()

Convert Graph to a libpysal.weights.W object

Returns:

libpysal.weights.W

representation of graph as a weights.W object

to_networkx()

Convert Graph to a networkx graph.

If Graph is symmetric, returns nx.Graph, otherwise returns a nx.DiGraph.

Returns:

networkx.Graph | networkx.DiGraph

Representation of libpysal Graph as networkx graph

to_parquet(path, **kwargs)

Save Graph to a Apache Parquet

Graph is serialized to the Apache Parquet using the underlying adjacency object stored as a Parquet table and custom metadata containing transformation.

Requires pyarrow package.

Parameters:

pathstr | pyarrow.NativeFile

path or any stream supported by pyarrow

**kwargs

additional keyword arguments passed to pyarrow.parquet.write_table

See also

read_parquet

transform(transformation)

Transformation of weights

Parameters:

transformationstr | callable()

Transformation method. The following are valid transformations.

• B – Binary

• R – Row-standardization (global sum \(=n\))

• D – Double-standardization (global sum \(=1\))

• V – Variance stabilizing

Alternatively, you can pass your own callable passed to self.adjacency.groupby(level=0).transform().

Returns:

Graph

transformed weights

Raises:

ValueError

Value error for unsupported transformation

property unique_ids

Unique IDs used in the Graph

property weights

Get weights dictionary

Returns:

dict

dict of tuples representing weights

Notes

It is recommended to work directly with Graph.adjacency() rather than using the Graph.weights().