readXStringColumns: Read one or more columns into XStringSet (e.g., DNAStringSet)...
In ShortRead: FASTQ input and manipulation

Description Usage Arguments Value Author(s) Examples

This function allows short read data components such as DNA sequence, quality scores, and read names to be read in to XStringSet (e.g., DNAStringSet, BStringSet) objects. One or several files of identical layout can be specified.

readXStringColumns(dirPath, pattern=character(0),
                   colClasses=list(NULL),
                   nrows=-1L, skip=0L,
                   sep = "\t", header = FALSE, comment.char="#")

`dirPath`	A character vector giving the directory path (relative or absolute) of files to be read.
`pattern`	The (`grep`-style) pattern describing file names to be read. The default (`character(0)`) reads all files in `dirPath`. All files are expected to have identical numbers of columns.
`colClasses`	A list of length equal to the number of columns in a file. Columns with corresponding `colClasses` equal to `NULL` are ignored. Other entries in `colClasses` are expected to be character strings describing the base class for the `XStringSet`. For instance a column of DNA sequences would be specified as `"DNAString"`. The column would be parsed into a `DNAStringSet` object.
`nrows`	A length 1 integer vector describing the maximum number of `XString` objects to read into the set. Reads may come from more than one file when `dirPath` and `pattern` parse several files and `nrow` is greater than the number of reads in the first file.
`skip`	A length 1 integer vector describing how many lines to skip at the start of each file.
`sep`	A length 1 character vector describing the column separator.
`header`	A length 1 logical vector indicating whether files include a header line identifying columns. If present, the header of the first file is used to name the returned values.
`comment.char`	A length 1 character vector, with a single character that, when appearing at the start of a line, indicates that the entire line should be ignored. Currently there is no way to use comment characters in other than the first position of a line.

A list, with each element containing an XStringSet object of the type corresponding to the non-NULL elements of colClasses.

Martin Morgan <mtmorgan@fhcrc.org>

## valid character strings for colClasses
names(slot(getClass("XString"), "subclasses"))

dirPath <- system.file('extdata', 'maq', package='ShortRead')

colClasses <- rep(list(NULL), 16)
colClasses[c(1, 15, 16)] <- c("BString", "DNAString", "BString")

## read one file
readXStringColumns(dirPath, "out.aln.1.txt", colClasses=colClasses)

## read all files into a single object for each column
res <- readXStringColumns(dirPath, colClasses=colClasses)