ScanBamParam-class: Parameters for scanning BAM files
In Bioconductor/Rsamtools: Binary alignment (BAM), FASTA, variant call (BCF), and tabix file import

ScanBamParam

R Documentation

Parameters for scanning BAM files

Description

Use ScanBamParam() to create a parameter object influencing what fields and which records are imported from a (binary) BAM file. Use of which requires that a BAM index file (<filename>.bai) exists.

Usage


# Constructor
ScanBamParam(flag = scanBamFlag(), simpleCigar = FALSE,
    reverseComplement = FALSE, tag = character(0), tagFilter = list(),
    what = character(0), which, mapqFilter=NA_integer_)

# Constructor helpers
scanBamFlag(isPaired = NA, isProperPair = NA, isUnmappedQuery = NA, 
    hasUnmappedMate = NA, isMinusStrand = NA, isMateMinusStrand = NA,
    isFirstMateRead = NA, isSecondMateRead = NA, isNotPrimaryRead = NA,
    isSecondaryAlignment = NA, isNotPassingQualityControls = NA,
    isDuplicate = NA, isSupplementaryAlignment = NA)

scanBamWhat()

# Accessors
bamFlag(object, asInteger=FALSE)
bamFlag(object) <- value
bamReverseComplement(object)
bamReverseComplement(object) <- value
bamSimpleCigar(object)
bamSimpleCigar(object) <- value
bamTag(object)
bamTag(object) <- value
bamTagFilter(object)
bamTagFilter(object) <- value
bamWhat(object)
bamWhat(object) <- value
bamWhich(object)
bamWhich(object) <- value
bamMapqFilter(object)
bamMapqFilter(object) <- value

## S4 method for signature 'ScanBamParam'
show(object)

# Flag utils
bamFlagAsBitMatrix(flag, bitnames=FLAG_BITNAMES)
bamFlagAND(flag1, flag2)
bamFlagTest(flag, value)

Arguments

`flag`	For `ScanBamParam`, an integer(2) vector used to filter reads based on their 'flag' entry. This is most easily created with the `scanBamFlag()` helper function. For `bamFlagAsBitMatrix`, `bamFlagTest` an integer vector where each element represents a 'flag' entry.
`simpleCigar`	A logical(1) vector which, when TRUE, returns only those reads for which the cigar (run-length encoded representation of the alignment) is missing or contains only matches / mismatches (`'M'`).
`reverseComplement`	A logical(1) vectors. BAM files store reads mapping to the minus strand as though they are on the plus strand. Rsamtools obeys this convention by default (`reverseComplement=FALSE`), but when this value is set to TRUE returns the sequence and quality scores of reads mapped to the minus strand in the reverse complement (sequence) and reverse (quality) of the read as stored in the BAM file. This might be useful if wishing to recover read and quality scores as represented in fastq files, but is NOT appropriate for variant calling or other alignment-based operations.
`tag`	A character vector naming tags to be extracted. A tag is an optional field, with arbitrary information, stored with each record. Tags are identified by two-letter codes, so all elements of `tag` must have exactly 2 characters.
`tagFilter`	A named `list` of atomic vectors. The name of each `list` element is the tag name (two-letter code), and the corresponding atomic vector is the set of acceptable values for the tag. Only reads with specified tags are included. `NULL`s, `NA`s, and empty strings are not allowed in the atomic vectors.
`what`	A character vector naming the fields to return `scanBamWhat()` returns a vector of available fields. Fields are described on the `scanBam` help page.
`mapqFilter`	A non-negative integer(1) specifying the minimum mapping quality to include. BAM records with mapping qualities less than `mapqFilter` are discarded.
`which`	A `GRanges`, `IntegerRangesList`, or any object that can be coerced to a `IntegerRangesList`, or missing object, from which a `IRangesList` instance will be constructed. Names of the `IRangesList` correspond to reference sequences, and ranges to the regions on that reference sequence for which matches are desired. Because data types are coerced to `IRangesList`, `which` does not include strand information (use the `flag` argument instead). Only records with a read overlapping the specified ranges are returned. All ranges must have ends less than or equal to 536870912. When one record overlaps two ranges in `which`, the record is returned twice.
`isPaired`	A logical(1) indicating whether unpaired (FALSE), paired (TRUE), or any (NA) read should be returned.
`isProperPair`	A logical(1) indicating whether improperly paired (FALSE), properly paired (TRUE), or any (NA) read should be returned. A properly paired read is defined by the alignment algorithm and might, e.g., represent reads aligning to identical reference sequences and with a specified distance.
`isUnmappedQuery`	A logical(1) indicating whether unmapped (TRUE), mapped (FALSE), or any (NA) read should be returned.
`hasUnmappedMate`	A logical(1) indicating whether reads with mapped (FALSE), unmapped (TRUE), or any (NA) mate should be returned.
`isMinusStrand`	A logical(1) indicating whether reads aligned to the plus (FALSE), minus (TRUE), or any (NA) strand should be returned.
`isMateMinusStrand`	A logical(1) indicating whether mate reads aligned to the plus (FALSE), minus (TRUE), or any (NA) strand should be returned.
`isFirstMateRead`	A logical(1) indicating whether the first mate read should be returned (TRUE) or not (FALSE), or whether mate read number should be ignored (NA).
`isSecondMateRead`	A logical(1) indicating whether the second mate read should be returned (TRUE) or not (FALSE), or whether mate read number should be ignored (NA).
`isNotPrimaryRead`	Deprecated; use `isSecondaryAlignment`.
`isSecondaryAlignment`	A logical(1) indicating whether alignments that are secondary (TRUE), are not (FALSE) or whose secondary status does not matter (NA) should be returned. A non-primary alignment (“secondary alignment” in the SAM specification) might result when a read aligns to multiple locations. One alignment is designated as primary and has this flag set to FALSE; the remainder, for which this flag is TRUE, are designated by the aligner as secondary.
`isNotPassingQualityControls`	A logical(1) indicating whether reads passing quality controls (FALSE), reads not passing quality controls (TRUE), or any (NA) read should be returned.
`isDuplicate`	A logical(1) indicating that un-duplicated (FALSE), duplicated (TRUE), or any (NA) reads should be returned. 'Duplicated' reads may represent PCR or optical duplicates.
`isSupplementaryAlignment`	A logical(1) indicating that non-supplementary (FALSE), supplementary (TRUE), or any (NA) reads should be returned. The SAM specification indicates that 'supplementary' reads are part of a chimeric alignment.
`object`	An instance of class `ScanBamParam`.
`value`	An instance of the corresponding slot, to be assigned to `object` or, for `bamFlagTest`, a `character(1)` name of the flag to test, e.g., “isUnmappedQuery”, from the arguments to `scanBamFlag`.
`asInteger`	logical(1) indicating whether ‘flag’ should be returned as an encoded integer vector (`TRUE`) or human-readable form (`FALSE`).
`bitnames`	Names of the flag bits to extract. Will be the colnames of the returned matrix.
`flag1`, `flag2`	Integer vectors containing ‘flag’ entries.

Objects from the Class

Objects are created by calls of the form ScanBamParam().

Slots

flag: Object of class integer encoding flags to be kept when they have their '0' (keep0) or '1' (keep1) bit set.
simpleCigar: Object of class logical indicating, when TRUE, that only 'simple' cigars (empty or 'M') are returned.
reverseComplement: Object of class logical indicating, when TRUE, that reads on the minus strand are to be reverse complemented (sequence) and reversed (quality).
tag: Object of class character indicating what tags are to be returned.
tagFilter: Object of class list (named) indicating tags to filter by, and the set of acceptable values for each tag.
what: Object of class character indicating what fields are to be returned.
which: Object of class IntegerRangesList indicating which reference sequence and coordinate reads must overlap.
mapqFilter: Object of class integer indicating the minimum mapping quality required for input, or NA to indicate no filtering.

Functions and methods

See 'Usage' for details on invocation.

Constructor:

ScanBamParam:: Returns a ScanBamParam object. The which argument to the constructor can be one of several different types, as documented above.

Accessors:

bamTag, bamTag<-: Returns or sets a character vector of tags to be extracted.
bamTagFilter, bamTagFilter<-: Returns or sets a named list of tags to filter by, and the set of their acceptable values.
bamWhat, bamWhat<-: Returns or sets a character vector of fields to be extracted.
bamWhich, bamWhich<-: Returns or sets a IntegerRangesList of bounds on reads to be extracted. A length 0 IntegerRangesList represents all reads.
bamFlag, bamFlag<-: Returns or sets an integer(2) representation of reads flagged to be kept or excluded.
bamSimpleCigar, bamSimpleCigar<-: Returns or sets a logical(1) vector indicating whether reads without indels or clipping be kept.
bamReverseComplement, bamReverseComplement<-: Returns or sets a logical(1) vector indicating whether reads on the minus strand will be returned with sequence reverse complemented and quality reversed.

Methods:

show: Compactly display the object.

Author(s)

Martin Morgan

Examples

## defaults
p0 <- ScanBamParam()

## subset of reads based on genomic coordinates
which <- IRangesList(seq1=IRanges(1000, 2000),
                     seq2=IRanges(c(100, 1000), c(1000, 2000)))
p1 <- ScanBamParam(what=scanBamWhat(), which=which)

## subset of reads based on 'flag' value
p2 <- ScanBamParam(what=scanBamWhat(),
                   flag=scanBamFlag(isMinusStrand=FALSE))

## subset of fields
p3 <- ScanBamParam(what=c("rname", "strand", "pos", "qwidth"))
                
## use
fl <- system.file("extdata", "ex1.bam", package="Rsamtools",
                  mustWork=TRUE)
res <- scanBam(fl, param=p2)[[1]]
lapply(res, head)

## tags; NM: edit distance; H1: 1-difference hits
p4 <- ScanBamParam(tag=c("NM", "H1"), what="flag")
bam4 <- scanBam(fl, param=p4)
str(bam4[[1]][["tag"]])

## tagFilter
p5 <- ScanBamParam(tag=c("NM", "H1"), tagFilter=list(NM=c(2, 3, 4)))
bam5 <- scanBam(fl, param=p5)
table(bam5[[1]][["tag"]][["NM"]])

## flag utils
flag <- scanBamFlag(isUnmappedQuery=FALSE, isMinusStrand=TRUE)

p6 <- ScanBamParam(what="flag")
bam6 <- scanBam(fl, param=p6)
flag6 <- bam6[[1]][["flag"]]
head(bamFlagAsBitMatrix(flag6[1:9]))
colSums(bamFlagAsBitMatrix(flag6))
flag
bamFlagAsBitMatrix(flag)

Bioconductor/Rsamtools documentation built on Oct. 31, 2024, 1:23 p.m.