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Count pairs of modified bases by distance and modification state

Source: R/countStatePairs.R
countStatePairs.Rd

For all pairs of bases with modification calls in a read, tabulate the number of pairs at a given distance with a given modification state.

Usage

countStatePairs(
  bamfile,
  regions = ".",
  modbase,
  threshUnmod = 0.5,
  threshMod = 0.5,
  windowSize = 200,
  minMapQ = 0,
  minAlignedLength = 0,
  BPPARAM = MulticoreParam(4L),
  verbose = FALSE
)

Arguments

bamfile

Character scalar with the path to a modBAM file, containing information about base modifications in MM and ML tags. The bamfile must have an index.

regions

A GRanges object specifying which genomic regions to extract the reads from. Alternatively, regions can be specified as a character vector (e.g. "chr1:1200-1300", "chr2:-6000", "chr1:10-", "chrM" or ".").

modbase

Character scalar defining the modified base.

threshUnmod, threshMod

Numeric scalars defining how to convert modification probabilities p to modification states. Bases with p < threshUnmod will be considered unmodified, and bases with p >= threshMod modified. All remaining bases will be ignored.

windowSize

Numeric scalar giving the maximum window size covering pairs of modified bases to consider in pair-counting mode. A window size of 1 corresponds to a single base, a size of 2 to directly adjacent bases, etc.

minMapQ

Numeric scalar giving the minimal mapping quality to include alignments in pair-counting mode.

minAlignedLength

Numeric scalar giving the minimal alignment length to include alignments in pair-counting mode.

BPPARAM

A BiocParallelParam object that controls the number of parallel CPU threads to use for decompressing bam records.

verbose

A logical scalar. If TRUE, report on progress.

Value

A DataFrame with windowSize rows and five columns.

Author

Charlotte Soneson, Michael Stadler

Examples

modbamfile <- system.file("extdata", "6mA_1_10reads.bam",
                          package = "footprintR")
res <- countStatePairs(bamfile = modbamfile,
                       regions = "chr1",
                       modbase = "a", windowSize = 300,
                       BPPARAM = BiocParallel::SerialParam())
res
#> DataFrame with 300 rows and 5 columns
#>             S unmod_unmod unmod_mod mod_unmod   mod_mod
#>     <integer>   <numeric> <numeric> <numeric> <numeric>
#> 1           1       27084         0         0      2461
#> 2           2        8877       281       340       408
#> 3           3        9131       441       439       264
#> 4           4        8140       399       403       282
#> 5           5        8565       485       493       164
#> ...       ...         ...       ...       ...       ...
#> 296       296        7399       701       615        63
#> 297       297        7097       654       584        60
#> 298       298        7342       680       650        66
#> 299       299        7222       673       654        70
#> 300       300        7196       642       640        65