## Coverage of a GRanges object:
gr <- GRanges(
        seqnames=Rle(c("chr1", "chr2", "chr1", "chr3"), c(1, 3, 2, 4)),
        ranges=IRanges(1:10, end=10),
        strand=Rle(strand(c("-", "+", "*", "+", "-")), c(1, 2, 2, 3, 2)),
        seqlengths=c(chr1=11, chr2=12, chr3=13))
cvg <- coverage(gr)
pcvg <- coverage(gr[strand(gr) == "+"])
mcvg <- coverage(gr[strand(gr) == "-"])
scvg <- coverage(gr[strand(gr) == "*"])
stopifnot(identical(pcvg + mcvg + scvg, cvg))
## Coverage of a GRangesList object:
gr1 <- GRanges(seqnames="chr2",
               ranges=IRanges(3, 6),
               strand = "+")
gr2 <- GRanges(seqnames=c("chr1", "chr1"),
               ranges=IRanges(c(7,13), width=3),
               strand=c("+", "-"))
gr3 <- GRanges(seqnames=c("chr1", "chr2"),
               ranges=IRanges(c(1, 4), c(3, 9)),
               strand=c("-", "-"))
grl <- GRangesList(gr1=gr1, gr2=gr2, gr3=gr3)
stopifnot(identical(coverage(grl), coverage(unlist(grl))))
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