gGraph-class | R Documentation |
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.
In all slots, nodes are uniquely identified by their name (reference is
taken from the row names of @coords
slot).
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.
gGraph
objects can be created
by calls to new("gGraph", ...)
, where '...' can be the following
arguments:
Related classes are:
% - graphNEL
(graph package): slot @graph
in gGraph
.
## create an empty object
new("gGraph")
## 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")
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