subset point data set by distance ranges

  Greetings
  I'm using R 2.8 with recent (last month) versions of the packages I need to
  use at present.

  I'm interested in examining hierarchical spatio-temporal patterns in a data
  set.  The data consist of 94 points (X, Y, UTM coordinates) at which catch
  rates  for  a  fish were recorded and there are also estimates of prey
  available for these fish at the same locations.  I have reason to believe
  that the relationships between predators and prey varies with spatial scale
  (nested processes).

  To test this hypothesis, I'd like to generate subsets of the points that are
  separated by distance ranges (1-50 km, 51-100 km, etc) so I can run Sncf
  (package ncf) on the subsets.

  I cannot find a way to do this with R code.  Getting a distance matrix is
  easy.  Using that to help generate a series of distance-based subsets is
  something I cannot figure out (without manually entering a list of all the
  point pairs).

cv <- rnorm(20) # phony coords
dim(cv) <- c(10,2)
alldist3 <- as.matrix( dist( cv ) ) # Euclidean
cd <- cut(alldist3,c( 0, 1, 2, 4, Inf) )
sapply(levels(cd), function(x) which(array(cd == x,dim(alldist3)),arr.ind=TRUE))

  Any suggestions would be appreciated.
  For what it's worth, I did post this question to R-sig-geo as well.
  Dave Warner
  David Warner
  Research Fishery Biologist
  USGS Great Lakes Science Center
  1451 Green Road
  Ann Arbor MI 48105
  734.214.9392