[R-sig-Geo] I NEED Help with this spatial polygon problems (REALLY) Thanks really thanks

[Roger Bivand]

On Wed, 1 Apr 2009, gianni lavaredo wrote:

> Hey All,
>
> I have this problem and I need really help to understand (my limit) . I have
> a polygon shape file and I need to calculate some index and select the
> polygon with correct index value. I DID this with library(PBSmapping), but I
> need to obtain new polygon shapefile
>
> singleGap <- readOGR(".", "singleGap")
> # Convert the SpatialPolygonDataFrame into a PolySet object for
> compatibility
> # with the so that PBSMapping package's geospatial functions
>
> singleGapPBS <- SpatialPolygons2PolySet(singleGap)
> # Calcula AREA
> singleGap.area <- calcArea(singleGapPBS)
> str(singleGap.area)
>
> # Calcula PERIMETER
> singleGap.perimeter <- calcLength(singleGapPBS)
> str(singleGap.perimeter)
>
> singleGap.Index <-
> data.frame(singleGap.area[,c(1,3)],singleGap.perimeter[,3])
> names(singleGap.Index)[3] = "perimeter"
> str(singleGap.Index)

Which says what? Is singleGap.Index[[1]] named area? Is it a vector or a 
data frame? I think that singleGap.Index isn't what you think it is, 
meaning that singleGap.Index$area is NULL, and subsetting will not work.

Roger

>
> singleGap.Index <- singleGap.Index[singleGap.Index$area >= 5
> |singleGap.Index$area < 1000,]
> NOW I TRYING SEVERAL METHOD BUT NOTHING. Thank, really thanks
>
> Gianni
>
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>
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-- 
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