joseph wrote:
why alignQuality is NA after readAligned() of a bowtie alignment file?

because Bowtie doesn't report alignment qualities. See

http://bowtie-bio.sourceforge.net/manual.shtml#algn_out

Martin


aln1 = readAligned("~/data", pattern="s_2.map", type="Bowtie")

aln1
class: AlignedRead
length: 4072324 reads; width: 34..34 cycles
chromosome: gi|89161210|ref|NC_000006.10|NC_000006 gi|89161210|ref|NC_000006.10|NC_000006 ... gi|89161205|ref|NC_000003.10|NC_000003 gi|89161205|ref|NC_000003.10|NC_000003 position: 20601560 20601583 ... 185508441 185508446 strand: + - ... + - alignQuality: NumericQuality alignData varLabels: mismatch
head(id(aln1))
  A BStringSet instance of length 6
    width seq
[1]    18 GAII:2:1:3:174#0/1
[2]    18 GAII:2:1:3:174#0/2
[3]    18 GAII:2:1:3:170#0/2
[4]    18 GAII:2:1:3:170#0/1
[5]    18 GAII:2:1:4:148#0/1
[6]    18 GAII:2:1:4:148#0/2
head(sread(aln1))
  A DNAStringSet instance of length 6
    width seq
[1]    34 CGTGTGTATGAGAAGGAGGGATATGAAGGAAGAT
[2]    34 CCACCCGACTTACTCTGCAATCCATCTTCCTTCA
[3]    34 AGCAGGTGCTGAGGTGGGAGGATCTAGCACCACC
[4]    34 CTGGTGCCTGGTGGTGCTAGCTCCTCCCACCTCA
[5]    34 TTTTCAAAACCATTCCTCAGTATCTTCAGGCATT
[6]    34 GGGCCAAGCACATTCAGGAGGTCAAATGCCTGAA
head(quality(aln1))
class: SFastqQuality
quality:
  A BStringSet instance of length 6
    width seq
[1]    34 ababa`aa`X_^``VYX_W][^\a]\W[MWV^V\
[2]    34 aababbaa\GG\[G^GJVb[I[\BBBBBBBBBBB
[3]    34 a`aa`WFRZMW]J[MWUL]TM[LWMTW\`U`_YR
[4]    34 a`a`aaaaaa_``[_V_`_]_____\_]N][_]]
[5]    34 abbb_aaaa`aaaa`aaa`Z[aaaaa__QWZZaa
[6]    34 ababbbabbab^MM^bbb_][M^bbZG^_^GR_b
head(alignQuality(aln1))
class: NumericQuality
quality: NA NA ... NA NA (6 total)
head(strand(aln1))
[1] + - + - + -
Levels: - + *
head(alignData(aln1))
An object of class "AlignedDataFrame"
  readName: 1
  varLabels and varMetadata description:
    mismatch: Comma-separated mismatch positions




sessionInfo()
R version 2.8.1 Patched (2009-03-03 r48046) i386-apple-darwin9.6.0 locale:
en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base other attached packages:
[1] ShortRead_1.1.51   lattice_0.17-20    BSgenome_1.11.13   Biostrings_2.11.44
[5] IRanges_1.1.55 loaded via a namespace (and not attached):
Error in x[["Version"]] : subscript out of bounds
In addition: Warning message:
In FUN(c("Biobase", "grid", "hwriter")[[3L]], ...) :
  no package 'hwriter' was found


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Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
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