[R-sig-Geo] Union sp polygons ID (rgoes and sp)

[Omphalodes Verna]

Thanks Roger!

No, there is no mistaking. This is kind of dissolve function. But I need overlapping / intersection of polygons, where common polygons have unique ID

Thanks




----- Original Message -----
From: Roger Bivand <Roger.Bivand at nhh.no>
To: Omphalodes Verna <omphalodes.verna at yahoo.com>
Cc: "r-sig-geo at r-project.org" <r-sig-geo at r-project.org>
Sent: Saturday, March 16, 2013 4:34 PM
Subject: Re: [R-sig-Geo] Union sp polygons ID (rgoes and sp)

On Sat, 16 Mar 2013, Omphalodes Verna wrote:

> Dear list.
> 
> I would like to do union of many polygons in R (rgeos) with ''gUnion'' function (in attached code only 5). Final result should be polygons with unique ID (using attached code it is), but when I plot them (colors by ID value), there are only 5 polygons. Please, give me some idea. Thanks to all, OV

Are you mistaking gUnion() for gUnaryUnion()?

gU = gUnaryUnion(SPLpoly, id=rep("1", length(SPLpoly)))

Roger

> 
> RCode:
> library(rgeos)
> library(sp)
> n <- 5
> xy <- cbind(runif(n), runif(n), runif(n), runif(n))
> LLine <- vector("list", n)
> LLines <- vector("list", n)
> for(i in 1:n) LLine[[i]] <- Line(rbind(xy[i, 1:2], xy[i, 3:4]))
> for(i in 1:n) LLines[[i]] <- Lines(LLine[[i]], ID = i)
> SPLines <- SpatialLines(LLines)
> SPLpoly <- gBuffer(SPLines, width = 0.05, byid = TRUE)
> plot(SPLines, col = getSLLinesIDSlots(SPLines))
> plot(SPLpoly, add = TRUE, col = getSLLinesIDSlots(SPLines))
> SPLpolyA <- SPLpoly
> SPLpolyB <- SPLpoly
> gU = gUnion(SPLpolyA, SPLpolyB,  byid = TRUE)
> plot(gU, col = rainbow(length(gU)))
> 
> 
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-- Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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