How to re-ID polygons with sapply instead of for loop

Question

I have a line of code that renames the id's of polygons in a SpatialPolygonsDataFrame by directly manipulating the ID slot of the polygon. I'm a bit slow when it comes to sapply, having used for loops for at least 20 years. Anyhow I have a piece of code that works using a for loop, but its really slow. I would like to replace it with a sapply command but can't figure it out. My code looks like this:

for(v in 1:nrow(SPoly)) {
    SPoly@polygons[[v]]@ID <- SPoly@data[v,3]
}

Can anyone suggest an sapply implementation of same?

Answer 1

sapply won't be faster in this case. Try spChFIDs instead (package sp):

SPoly <- spChFIDs(SPoly, as.character(SPoly@data[, 3]))

From ?spChFIDs:

change feature IDs in spatial objects

Description

When the feature IDs need to be changed in SpatialLines* or SpatialPolygons* objects, these methods may be used. The new IDs should be a character vector of unique IDs of the correct length.