fl <- system.file("extdata", "ex1.bam", package = "Rsamtools")
  gr <- GRanges(c(rep("seq2", 3), "seq1"), 
                IRanges(c(75, 1, 100, 1), width = 2))
  ## Ranges are packed by order within chromosome and grouped
  ## around gaps greater than 'inter_range_len'. See ?pack for details.
  pk <- pack(gr, inter_range_len = 25)
  ## FUN computes coverage for the range passed as 'rng'.
  FUN <- function(rng, fl, param) {
      requireNamespace("GenomicAlignments") ## for bamWhich() and coverage()
      Rsamtools::bamWhich(param) <- rng
      GenomicAlignments::coverage(Rsamtools::BamFile(fl), param=param)[rng]
  } 
  ## Compute coverage on the packed ranges.
  dat <- bplapply(as.list(pk), FUN, fl = fl, param = ScanBamParam())
  ## The result list contains RleLists of coverage.
  lapply(dat, class)
  ## unpack() transforms the results back to the order of 
  ## the original ranges (i.e., unpacked 'gr').
  unpack(dat, pk)
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