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




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