methylPipe (version 1.6.2)

mapBSdata2GRanges: Retrieve mC calls for a GRanges set of genomic regions given a BSdata object for a sample

Description

mapBSdata2GRanges retrieves mC calls for a GRanges given a BSdata object for a sample. mapBSdata2GRangesBin does the same for each bin of each genomic region.

Usage

mapBSdata2GRanges(GenoRanges, Sample, context='all', mC=1, depth=0, pValue=1)
mapBSdata2GRangesBin(GenoRanges, Sample, context='all', mC=1, depth=0, pValue=1, nbins)

Arguments

GenoRanges

An object of class GRanges

Sample

An object of class BSdata

context

character; one of: all, CG, CHG or CHH

mC

numeric; the minumum number of reads with C (DNA-methylation events) at a given cytosine genomic position

depth

numeric; the minimum number of total reads at a given cytosine genomic position

pValue

numeric; the minimum binomial pValue for an mC call at a given cytosine genomic position

nbins

numeric; the number of bins in which Genomic regions are divided

Value

• A list is returned. The length of the list is equal to the length of the GRanges. For each list item either NA, 0 or a data frame are returned. 0 means that the region contains unmethylated DNA methylation sites, whereas NA indicates that the region or some part of region was not covered by the sequencing. If a data frame is returned, it has the following columns: chromosome assignment (in the form chr1, .., chr22, chrX, chrY, chrM, chrC), genomic position (positive integer), strand (either - or +), methylation sequence context (either CG, CHG or CHH), number (>0) of sequencing reads with C calls at that genomic position, number of sequencing reads with T calls at that genomic position, binomial pvalue (-10*log10(pvalue)) for calling a mC at that position.

Details

DNA-methylation data contained for a sample within a BSdata object is extracted for the set of genomic regions of a GRanges (and in particular for each bin using the mapBSdata2GRangesBin method). It is also possible to restrict the mC sequence context, to specify the minimal number of reads with C events at a given cytosine genomic position, to specify the minimum depth of sequencing and binomial pValue for the mC calls. A region with no mC will be defined unmethylated (0 is returned for that region). However, if it is overlapping with at least one uncovered region then it is defined non evaluable (NA is retuned).

Examples

require(BSgenome.Hsapiens.UCSC.hg18)
uncov_GR <- GRanges(Rle('chr20'), IRanges(c(14350,69251,84185), c(18349,73250,88184)))
H1data <- system.file('extdata', 'H1_chr20_CG_10k_tabix_out.txt.gz', package='methylPipe')
H1.db <- BSdata(file=H1data, uncov=uncov_GR, org=Hsapiens)
gr_file <- system.file('extdata', 'GR_chr20.Rdata', package='methylPipe')
load(gr_file)
res <- mapBSdata2GRanges(GenoRanges=GR_chr20, Sample=H1.db, context='CG', mC=1, depth=0, pValue=1)
resbin <- mapBSdata2GRangesBin(GenoRanges=GR_chr20, Sample=H1.db, context='CG', mC=1, depth=0, pValue=1, nbins=2)