Plot geographic regions defined as polygons

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Description

Produces plots of geographic regions defined by polygons, optionally filling the polygons with a color or grey shade dependent on a covariate.

Usage

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polys.plot(pc,z=NULL,scheme="heat",lab="",...)

Arguments

pc

A named list of matrices. Each matrix has two columns. The matrix rows each define the vertex of a boundary polygon. If a boundary is defined by several polygons, then each of these must be separated by an NA row in the matrix. See mrf for an example.

z

A vector of values associated with each area (item) of pc. If the vector elements have names then these are used to match elements of z to areas defined in pc. Otherwise pc and z are assumed to be in the same order. If z is NULL then polygons are not filled.

scheme

One of "heat" or "grey", indicating how to fill the polygons in accordance with the value of z.

lab

label for plot.

...

other arguments to pass to plot (currently only if z is NULL).

Details

Any polygon within another polygon counts as a hole in the area. Further nesting is dealt with by treating any point that is interior to an odd number of polygons as being within the area, and all other points as being exterior. The routine is provided to facilitate plotting with models containing mrf smooths.

Value

Simply produces a plot.

Author(s)

Simon Wood simon.wood@r-project.org

See Also

mrf and columb.polys.

Examples

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## see also ?mrf for use of z
require(mgcv)
data(columb.polys)
polys.plot(columb.polys)

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