gData-class | R Documentation |
The class gData
is a formal (S4) class storing georeferenced data,
consisting in a set of locations (longitude and latitude) where one or
several variables have been measured. These data are designed to be matched
against a gGraph object, each location being assigned to the
closest node of the gGraph object.
Note that for several operations on a gData
object, the
gGraph object to which it is linked will have to be present in
the same environment.
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.id
a vector of character strings giving the name of the nodes (of the gGraph object) associated to the locations.
data
any kind of data associated to the locations in coords. For matrix-like objects, rows should correspond to locations.
gGraph.name
a character string the name of the gGraph object against which the object is matched.
Note
that none of these is mandatory: new("gData")
would work, and create
an empty gGraph
object. Also note that a finer matching of locations
against the nodes of a gGraph
object can be achieved after creating
the object, for instance using the closestNode
method.
gData
objects can be created
by calls to new("gData", ...)
, where '...' can be the following
arguments:
Related class:
- gGraph
hgdp
## plot data
plot(worldgraph.40k, pch = "")
points(hgdp)
## subset and plot data
onlyNorth <- hgdp[hgdp@data$Latitude > 0] # only northern populations
plot(worldgraph.40k, reset = TRUE)
abline(h = 0) # equator
points(onlyNorth, pch.node = 20, cex = 2, col.node = "purple")
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