R help - Jul 2012 - Dissolve polygon

Hi,

I am working with  a SpatialPolygonsDataFrame of many islands. There are a
lot of polygons (islands) composing my SpatialPolygonsDataFrame.
I want to extract the elevation of each island.
I need to separate the different polygons (like dissolve function in
arcgis), to have the elevation of each island.
Do you have any idea how can I do that ? 
I already read a lot of forum, and read the maptools package but I did not
find something useful for my problem.
Coordinates:
        min       max
x  40.32140 63.500179
y -25.60895 -3.711519
Is projected: FALSE 
proj4string : [+proj=longlat +ellps=WGS84 +no_defs]
Data attributes:
                                      NAME             TYPE  
 Madagascar and the Indian Ocean Islands:1   hotspot_area:1  
                                                NAME_TYPE
 Madagascar and the Indian Ocean Islands_hotspot_area:1  
                                     LEGEND 
 Madagascar and the Indian Ocean Islands:1  
> class(hot)
[1] "SpatialPolygonsDataFrame"
attr(,"package")
[1] "sp"

Thanks a lot for your help,

C?line




--
View this message in context:
http://r.789695.n4.nabble.com/Dissolve-polygon-tp4637234.html
Sent from the R help mailing list archive at Nabble.com.

On Fri, Jul 20, 2012 at 4:51 PM, Celine <bellard.celine at gmail.com>
wrote:
> Hi,
>
> I am working with  a SpatialPolygonsDataFrame of many islands. There are a
> lot of polygons (islands) composing my SpatialPolygonsDataFrame.
> I want to extract the elevation of each island.
 Is each island a row in your SPDF? Or is it just one row, with lots
of island polygons? What does dim(hot) (assuming 'hot' is your SPDF)
say?
> I need to separate the different polygons (like dissolve function in
> arcgis), to have the elevation of each island.
 If each island is a row, then its easy, if each island is a separate
loop in a single row, a bit trickier.

 How are you going to get the elevation? Do you have a separate data
source, such as a grid of elevations?

 Also, try hopping over to the R-sig-geo mailing list. For everything spatial.

 Barry

blog: http://geospaced.blogspot.com/
web: http://www.maths.lancs.ac.uk/~rowlings
web: http://www.rowlingson.com/
twitter: http://twitter.com/geospacedman
pics: http://www.flickr.com/photos/spacedman