VariantAnnotation (version 1.18.5)

summarizeVariants: Summarize variants by sample

Description

Variants in a VCF file are overlaped with an annotation region and summarized by sample. Genotype information in the VCF is used to determine which samples express each variant.

Usage

"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)
"summarizeVariants"(query, subject, mode, ...)

Arguments

query

A TxDb or GRangesList object that serves as the annotation. GFF files can be converted to TxDb objects with makeTxDbFromGFF() in the GenomicFeatures package.

subject

A VCF object containing the variants.

mode

mode can be a VariantType class or the name of a function.

When mode is a VariantType class, counting is done with locateVariants and counts are summarized transcript-by-sample. Supported VariantType classes include CodingVariants, IntronVariants, FiveUTRVariants, ThreeUTRVariants, SpliceSiteVariants or PromoterVariants. AllVariants() and IntergenicVariants are not supported. See ?locateVariants for more detail on the variant classes.

mode can also be the name of any counting function that outputs a Hits object. Variants will be summarized by the length of the GRangesList annotation (i.e., 'length-of-GRangesList'-by-sample).

...

Additional arguments passed to methods such as

ignore.strand

A logical indicating if strand should be igored when performing overlaps.

Value

A RangedSummarizedExperiment object with count summaries in the assays slot. The rowRanges contains the annotation used for counting. Information in colData and metadata are taken from the VCF file.

Details

summarizeVariants uses the genotype information in a VCF file to determine which samples are positive for each variant. Variants are overlapped with the annotation and the counts are summarized annotation-by-sample. If the annotation is a GRangesList of transcripts, the count matrix will be transcripts-by-sample. If the GRangesList is genes, the count matrix will be gene-by-sample.

• Counting with locateVariants() :

Variant counts are always summarized transcript-by-sample. When query is a GRangesList, it must be compatible with the VariantType-class given as the mode argument. The list below specifies the appropriate GRangesList for each mode.

CodingVariants :

coding (CDS) by transcript

IntronVariants :

introns by transcript

FiveUTRVariants :

five prime UTR by transcript

ThreeUTRVariants :

three prime UTR by transcript

SpliceSiteVariants :

introns by transcript

PromoterVariants :

list of transcripts

When query is a TxDb, the appropriate region-by-transcript GRangesList listed above is extracted internally and used as the annotation.

Counting with a user-supplied function :

subject must be a GRangesList and mode must be the name of a function. The count function must take 'query' and 'subject' arguments and return a Hits object. Counts are summarized by the outer list elements of the GRangesList.

See Also

readVcf, predictCoding locateVariants summarizeVariants,

Examples

  library(TxDb.Hsapiens.UCSC.hg19.knownGene)
  txdb <- TxDb.Hsapiens.UCSC.hg19.knownGene 

  ## Read variants from VCF.
  fl <- system.file("extdata", "chr22.vcf.gz", package="VariantAnnotation")
  vcf <- readVcf(fl, "hg19")
  ## Rename seqlevels to match TxDb; confirm the match.
  seqlevels(vcf) <- paste0("chr", seqlevels(vcf)) 
  intersect(seqlevels(vcf), seqlevels(txdb))

  ## ----------------------------------------
  ## Counting with locateVariants()
  ## ----------------------------------------
  ## TxDb as the 'query'
  coding1 <- summarizeVariants(txdb, vcf, CodingVariants())
  colSums(assays(coding1)$counts)

  ## GRangesList as the 'query'
  cdsbytx <- cdsBy(txdb, "tx")
  coding2 <- summarizeVariants(cdsbytx, vcf, CodingVariants()) 

  stopifnot(identical(assays(coding1)$counts, assays(coding2)$counts))

  ## Promoter region variants summarized by transcript
  tx <- transcripts(txdb)
  txlst <- splitAsList(tx, seq_len(length(tx)))
  promoter <- summarizeVariants(txlst, vcf, 
                                PromoterVariants(upstream=100, downstream=10))
  colSums(assays(promoter)$counts)

  ## ----------------------------------------
  ## Counting with findOverlaps() 
  ## ----------------------------------------

  ## Summarize all variants by transcript
  allvariants <- summarizeVariants(txlst, vcf, findOverlaps)
  colSums(assays(allvariants)$counts)