[R-sig-Geo] plotting Polygon (sp)

[Roger Bivand]

On Tue, 8 Jun 2010, Sebastian P. Luque wrote:

> Hi,
>
> Using the example from the vignette "sp" (section 7.1):

Well, not really, because the example on p. 19 builds a SpatialPolygons 
object, for which there is a plot() method. There is no plot() method for 
Polygon or Polygons objects exposed at the user level, mostly because of 
plot order and hole handling issues.

Roger

>
> ---<--------------------cut here---------------start------------------->---
> R> sr1
> An object of class "Polygon"
> Slot "labpt":
> [1] 2.697 3.545
>
> Slot "area":
> [1] 5.5
>
> Slot "hole":
> [1] TRUE
>
> Slot "ringDir":
> [1] -1
>
> Slot "coords":
>     [,1] [,2]
> [1,]    2    2
> [2,]    4    3
> [3,]    4    5
> [4,]    1    4
> [5,]    2    2
>
> R> plot(sr1)
> Error in as.double(y) :
>  cannot coerce type 'S4' to vector of type 'double'
> R> showMethods("plot")
> Function: plot (package graphics)
> x="ANY", y="ANY"
> x="Polygon", y="missing"
>    (inherited from: x="ANY", y="ANY")
> x="SpatialLines", y="missing"
> x="Spatial", y="missing"
> x="SpatialPoints", y="missing"
> x="SpatialPolygons", y="missing"
>
> R> sessionInfo()
> R version 2.11.1 (2010-05-31)
> x86_64-pc-linux-gnu
>
> locale:
> [1] LC_CTYPE=en_CA.UTF-8       LC_NUMERIC=C               LC_TIME=en_CA.UTF-8
> [4] LC_COLLATE=en_CA.UTF-8     LC_MONETARY=C              LC_MESSAGES=en_CA.UTF-8
> [7] LC_PAPER=en_CA.UTF-8       LC_NAME=C                  LC_ADDRESS=C
> [10] LC_TELEPHONE=C             LC_MEASUREMENT=en_CA.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] rgdal_0.6-27    maptools_0.7-34 foreign_0.8-40  mapdata_2.1-2   maps_2.1-3
> [6] sp_0.9-64       slmisc_0.7.6    lattice_0.18-8
>
> loaded via a namespace (and not attached):
> [1] grid_2.11.1  tools_2.11.1
> ---<--------------------cut here---------------end--------------------->---
>
> Why is plot() failing with that error?
>
>
> Cheers,
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no