Spatial morphers form spatial add-ons to the set of
morphers provided by tidygraph. These
functions are not meant to be called directly. They should either be passed
into morph to create a temporary alternative
representation of the input network. Such an alternative representation is a
list of one or more network objects. Single elements of that list can be
extracted directly as a new network by passing the morpher to
convert instead, to make the changes lasting rather
than temporary. Alternatively, if the morphed state contains multiple
elements, all of them can be extracted together inside a
tbl_df by passing the morpher to
crystallise.
to_spatial_directed(x)to_spatial_explicit(x, ...)
to_spatial_shortest_paths(x, ...)
to_spatial_simple(x, remove_parallels = TRUE, remove_loops = TRUE)
to_spatial_smooth(x, store_orig_data = FALSE)
to_spatial_subdivision(x)
to_spatial_subset(x, ..., subset_by = NULL)
to_spatial_transformed(x, ...)
An object of class sfnetwork.
Arguments to be passed on to other functions. See the description of each morpher for details.
Should parallel edges be removed. Defaults to
TRUE.
Should loops be remove. Defaults to TRUE.
Whenever multiple features (i.e. nodes and/or edges)
are merged into a single feature during morphing, should the data of the
original features be stored as an attribute of the new feature, in a column
named .orig_data. This is in line with the design principles of
tidygraph. Defaults to FALSE.
Whether to create subgraphs based on nodes or edges.
Either a morphed_sfnetwork, which is a list of one or more
sfnetwork objects, or a morphed_tbl_graph, which is a
list of one or more tbl_graph objects. See the
description of each morpher for details.
to_spatial_directed: Make a network directed in the direction given
by the linestring geometries of the edges. Differs from
to_directed, which makes a network directed based
on the node indices given in the from and to columns. In
undirected networks these indices may not correspond with the endpoints of
the linestring geometries. Returns a morphed_sfnetwork containing a
single element of class sfnetwork. This morpher requires edges
to be spatially explicit. If not, use to_directed.
to_spatial_explicit: Create linestring geometries between source
and target nodes of edges. If the edges data can be directly converted to
an object of class sf using st_as_sf,
extra arguments can be provided as ... and will be forwarded to
st_as_sf internally. Otherwise, straight lines will be
drawn between the source and target node of each edge. Returns a
morphed_sfnetwork containing a single element of class
sfnetwork.
to_spatial_shortest_paths: Limit a network to those nodes and edges that
are part of the shortest path between two nodes. ... is evaluated in
the same manner as st_network_paths with
type = 'shortest'. Returns a morphed_sfnetwork that may
contain multiple elements of class sfnetwork, depending on
the number of requested paths. When unmorphing only the first instance of
both the node and edge data will be used, as the the same node and/or edge
can be present in multiple paths.
to_spatial_simple: Remove loops and parallel edges. Returns a
morphed_sfnetwork containing a single element of class
sfnetwork.
to_spatial_smooth: Construct a smoothed version of the network by
iteratively removing pseudo nodes, while preserving the connectivity of the
network. In the case of directed networks, pseudo nodes are those nodes that
have only one incoming and one outgoing edge. In undirected networks, pseudo
nodes are those nodes that have two incident edges. Connectivity of the
network is preserved by concatenating the incident edges of each removed
pseudo node. Returns a morphed_sfnetwork containing a single element
of class sfnetwork.
to_spatial_subdivision: Construct a subdivision of the network by
subdividing edges at each interior point that is equal to any
other interior or boundary point in the edges table. Interior points in this
sense are those points that are included in their linestring geometry
feature but are not endpoints of it, while boundary points are the endpoints
of the linestrings. The network is reconstructed after subdivision such that
edges are connected at the points of subdivision. Returns a
morphed_sfnetwork containing a single element of class
sfnetwork. This morpher requires edges to be spatially
explicit.
to_spatial_subset: Subset the network by applying a spatial
filter, i.e. a filter on the geometry column based on a spatial predicate.
... is evaluated in the same manner as st_filter.
Returns a morphed_sfnetwork containing a single element of class
sfnetwork. For filters on an attribute column, use
to_subgraph.
to_spatial_transformed: Transform the geospatial coordinates of the
network into a different coordinate reference system. ... is
evaluated in the same manner as st_transform.
Returns a morphed_sfnetwork containing a single element of class
sfnetwork.
It also possible to create your own morphers. See the documentation
of morph for the requirements for custom morphers.
The vignette on spatial morphers.
# NOT RUN {
library(sf, quietly = TRUE)
library(tidygraph, quietly = TRUE)
net = as_sfnetwork(roxel, directed = FALSE) %>%
st_transform(3035)
# Temporary changes with morph and unmorph.
net %>%
activate("edges") %>%
mutate(weight = edge_length()) %>%
morph(to_spatial_shortest_paths, from = 1, to = 10) %>%
mutate(in_paths = TRUE) %>%
unmorph()
# Lasting changes with convert.
net %>%
activate("edges") %>%
mutate(weight = edge_length()) %>%
convert(to_spatial_shortest_paths, from = 1, to = 10)
# }
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