Formal class

The class gGraph is a formal (S4) class storing geographic data.
Such data are composed of a set of geographic coordinates of vertices (or 'nodes'), and a graph describing connectivity between these vertices. Data associated to the nodes can also be stored ('nodes attributes'), as well as meta-information used when plotting the object, or when computing weights associated to the edges based on nodes attributes.

Details

In all slots, nodes are uniquely identified by their name (reference is taken from the row names of @coords slot).

Slots

coords

a matrix of spatial coordinates with two columns, being respectively longitude (from -180 to 180) and latitude. Positive numbers are intended as 'east' and 'north', respectively.

nodes.attr

a data.frame whose rows are nodes, and whose columns are different variables associated to the nodes.

meta

list, most likely containing named data.frames (see Slots).

graph

an object of the class graphNEL, from the graph package (see class?graphNEL), describing connectivity among nodes.

Note that none of these is mandatory: new("gGraph") would work, and create an empty gGraph object.

Objects from the class gGraph

gGraph objects can be created by calls to new("gGraph", ...), where '...' can be the following arguments:

Examples


## create an empty object
new("gGraph")
#> 
#> === gGraph object ===
#> 
#> @coords: spatial coordinates of 0 nodes
#>      lon lat
#> 
#> @nodes.attr: 0 nodes attributes
#> data frame with 0 columns and 0 rows
#> 
#> @meta: list of meta information with 0 items
#> 
#> @graph:
#> A graphNEL graph with undirected edges
#> Number of Nodes = 0 
#> Number of Edges = 0 


## plotting the object
plot(rawgraph.10k, reset = TRUE)


## zooming in
geo.zoomin(list(x = c(-6, 38), y = c(35, 73)))
title("Europe")


## to play interactively with graphics, use:
# geo.zoomin()
# geo.zoomout()
# geo.slide()
# geo.back()

## defining a new object restrained to visible nodes
x <- rawgraph.10k[isInArea(rawgraph.10k)]
plot(x, reset = TRUE, edges = TRUE)
title("x does just contain these visible nodes.")


## define weights for edges
x <- setCosts(x, attr.name = "habitat", method = "prod")
plot(x, edges = TRUE)
title("costs defined by habitat (land/land=1, other=100)")


## drop 'dead edges' (i.e. with weight 0)
x <- dropDeadEdges(x, thres = 10)
plot(x, edges = TRUE)
title("after droping edges with null weight")

Formal class "gGraph"

Details

Slots

Objects from the class gGraph

See also

Examples