Assign node attributes from a polygon layer

The function assignByPolygon uses information from a GIS polygon shapefile to define node attributes. For each node, information is retrieved from the layer and assigned to that node.

Usage

assignByPolygon(x, ...)

# S4 method for class 'matrix'
assignByPolygon(x, layer = "world", attr = "all", ...)

# S4 method for class 'data.frame'
assignByPolygon(x, layer = "world", attr = "all", ...)

# S4 method for class 'numeric'
assignByPolygon(x, layer = "world", attr = "all", ...)

# S4 method for class 'list'
assignByPolygon(x, layer = "world", attr = "all", ...)

# S4 method for class 'gGraph'
assignByPolygon(x, layer = "world", attr = "all", ...)

# S4 method for class 'gData'
assignByPolygon(x, layer = "world", attr = "all", ...)

Arguments

x

a matrix, data.frame, list, valid gGraph, or valid gData object. For matrix and data.frame, input must have two columns giving longitudes and latitudes. For list, input must have two components being vectors of longitudes and latitudes.

...

further arguments passed to other methods (currently unused).

layer

a shapefile of class sf (see sf::st_read to import a GIS shapefile). Alternatively, "world" to use the built-in world shapefile.

attr

a character vector of variable names to extract from the layer. Use "all" to extract all available variables.

Value

For matrix, data.frame, or list input: a data.frame with one row per location and one column per requested variable. For gGraph input: a gGraph object with new node attributes added to @nodes.attr. For gData input: a gData object with new data added to @data.

Details

Nodes can be specified as a matrix, data.frame, list, gGraph, or gData object. Outputs match the input format.

The gGraph method can be memory-intensive for large graphs since it assigns attributes to all nodes.

Functions

• assignByPolygon(matrix): Method for matrix input

• assignByPolygon(data.frame): Method for data.frames input

• assignByPolygon(numeric): Method for numeric vector input

• assignByPolygon(list): Method for numeric list input

• assignByPolygon(gGraph): Method for gGraph objects

• assignByPolygon(gData): Method for gData objects

Note

The gGraph method should be carefully used, output is going to be heavy.

See also

findLand to find which locations are on land. assignByRaster to assign attributes from raster data.

Examples

plot(worldgraph.10k, reset = TRUE)
#> Spherical geometry (s2) switched off

#> Spherical geometry (s2) switched on

## retrieve continent info for all nodes
## (might take a few seconds)
x <- assignByPolygon(worldgraph.10k, layer = "world", attr = "continent")
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_intersects assumes that they
#> are planar
#> Spherical geometry (s2) switched on
x
#> 
#> === gGraph object ===
#> 
#> @coords: spatial coordinates of 10242 nodes
#>         lon       lat
#> 1 -180.0000  90.00000
#> 2  144.0000 -90.00000
#> 3  -33.7806  27.18924
#> ...
#> 
#> @nodes.attr: 2 nodes attributes
#>   habitat continent
#> 1     sea      <NA>
#> 2     sea      <NA>
#> 3     sea      <NA>
#> ...
#> 
#> @meta: list of meta information with 2 items
#> [1] "$colors" "$costs" 
#> 
#> @graph:
#> A graphNEL graph with undirected edges
#> Number of Nodes = 10242 
#> Number of Edges = 6954 
table(getNodesAttr(x, attr.name = "continent"))
#> continent
#>        Africa    Antarctica          Asia        Europe North America 
#>           603           242           628           455           481 
#>       Oceania South America 
#>           170           361 


## subset Africa
temp <- getNodesAttr(x, attr.name = "continent") == "Africa"
temp[is.na(temp)] <- FALSE
x <- x[temp]
plot(x, reset = TRUE)
#> Spherical geometry (s2) switched off

#> Spherical geometry (s2) switched on