alphabetByCycle: Summarize nucleotide, amino acid, or quality scores by cycle
In ShortRead: FASTQ input and manipulation

Description Usage Arguments Details Value Author(s) See Also Examples

alphabetByCycle summarizes nucleotides, amino acid, or qualities by cycle, e.g., returning the number of occurrences of each nucleotide A, T, G, C across all reads from 36 cycles of a Solexa lane.

1	alphabetByCycle(stringSet, alphabet, ...)

`stringSet`	A R object representing the collection of reads, amino acid sequences, or quality scores, to be summarized.
`alphabet`	The alphabet (character vector of length 1 strings) from which the sequences in `stringSet` are composed. Methods often define an appropriate alphabet, so that the user does not have to provide one.
`...`	Additional arguments, perhaps used by methods defined on this generic.

The default method requires that stringSet extends the XStringSet class of Biostrings.

The following method is defined, in addition to methods described in class-specific documentation:

alphabetByCycle: signature(stringSet = "BStringSet"): this method uses an alphabet spanning all ASCII characters, codes 1:255.

A matrix with number of rows equal to the length of alphabet and columns equal to the maximum width of reads or quality scores in the string set. Entries in the matrix are the number of times, over all reads of the set, that the corresponding letter of the alphabet (row) appeared at the specified cycle (column).

Martin Morgan

The IUPAC alphabet in Biostrings.

http://www.bioperl.org/wiki/FASTQ_sequence_format for the BioPerl definition of fastq.

Solexa documentation 'Data analysis - documentation : Pipeline output and visualisation'.

showMethods("alphabetByCycle")

sp <- SolexaPath(system.file('extdata', package='ShortRead'))
rfq <- readFastq(analysisPath(sp), pattern="s_1_sequence.txt")
alphabetByCycle(sread(rfq))

abcq <- alphabetByCycle(quality(rfq))
dim(abcq)
## 'high' scores, first and last cycles
abcq[64:94,c(1:5, 32:36)]