seqlengths <- c(chr1=60, chr2=20, chr3=25)

## Create 5 tiles:
tiles <- tileGenome(seqlengths, ntile=5)
tiles
elementNROWS(tiles)  # tiles 3 and 4 contain 2 ranges

width(tiles)
## Use sum() on this IntegerList object to get the effective tile
## widths:
sum(width(tiles))  # each tile covers exactly 21 genomic positions

## Create 9 tiles:
tiles <- tileGenome(seqlengths, ntile=9)
elementNROWS(tiles)  # tiles 6 and 7 contain 2 ranges

table(sum(width(tiles)))  # some tiles cover 12 genomic positions,
                          # others 11

## Specify the tile width:
tiles <- tileGenome(seqlengths, tilewidth=20)
length(tiles)  # 6 tiles
table(sum(width(tiles)))  # effective tile width is <= specified

## Specify the tile width and cut the last tile in each chromosome:
tiles <- tileGenome(seqlengths, tilewidth=24,
                    cut.last.tile.in.chrom=TRUE)
tiles
width(tiles)  # each tile covers exactly 24 genomic positions, except
              # the last tile in each chromosome

## Partition a genome by chromosome ("natural partitioning"):
tiles <- tileGenome(seqlengths, tilewidth=max(seqlengths),
                    cut.last.tile.in.chrom=TRUE)
tiles  # one tile per chromosome

## sanity check
stopifnot(all.equal(setNames(end(tiles), seqnames(tiles)), seqlengths))