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 an idea how can I do that ?

dim(hot)
[1] 10945     5

class(hot)
[1] "SpatialLinesDataFrame"
attr(,"package")
[1] "sp"

Thanks in advance for your help,

C?line