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Calculate ArchR-compatible per-cell QC statistics

Source: R/atac_utils.R
qc_scATAC.Rd

Calculate ArchR-compatible per-cell QC statistics

Usage

qc_scATAC(fragments, genes, blacklist)

Arguments

fragments

IterableFragments object

genes

Gene coordinates given as GRanges, data.frame, or list. See help("genomic-ranges-like") for details on format and coordinate systems. Required attributes:

  • chr, start, end: genomic position

blacklist

Blacklisted regions given as GRanges, data.frame, or list. See help("genomic-ranges-like") for details on format and coordinate systems. Required attributes:

  • chr, start, end: genomic position

Value

data.frame with QC data

Details

This implementation mimics ArchR's default parameters. For uses requiring more flexibility to tweak default parameters, the best option is to re-implement this function with required changes. Output columns of data.frame:

  • cellName: cell name for each cell

  • nFrags: number of fragments per cell

  • subNucleosomal, monoNucleosomal, multiNucleosomal: number of fragments of size 1-146bp, 147-254bp, and 255bp + respectively. equivalent to ArchR's nMonoFrags, nDiFrags, nMultiFrags respectively

  • TSSEnrichment: AvgInsertInTSS / max(AvgInsertFlankingTSS, 0.1), where AvgInsertInTSS is ReadsInTSS / 101 (window size), and AvgInsertFlankingTSS is ReadsFlankingTSS / (100*2) (window size). The max(0.1) ensures that very low-read cells do not get assigned spuriously high TSSEnrichment.

  • ReadsInPromoter: Number of reads from 2000bp upstream of TSS to 101bp downstream of TSS

  • ReadsInBlacklist: Number of reads in the provided blacklist region

  • ReadsInTSS: Number of reads overlapping the 101bp centered around each TSS

  • ReadsFlankingTSS: Number of reads overlapping 1901-2000bp +/- each TSS

Differences from ArchR: Note that ArchR by default uses a different set of annotations to derive TSS sites and promoter sites. This function uses just one annotation for gene start+end sites, so must be called twice to exactly re-calculate the ArchR QC stats.

ArchR's PromoterRatio and BlacklistRatio are not included in the output, as they can be easily calculated from ReadsInPromoter / nFrags and ReadsInBlacklist / nFrags. Similarly, ArchR's NucleosomeRatio can be calculated as (monoNucleosomal + multiNucleosomal) / subNucleosomal.