readTable

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Reads a file in table format

Reads a file in table format and creates a data frame from it, with cases corresponding to lines and variables to fields in the file.

WARNING: This method is very much in an alpha stage. Expect it to change.

This method is an extension to the default read.table function in R. It is possible to specify a column name to column class map such that the column classes are automatically assigned from the column header in the file.

In addition, it is possible to read any subset of rows. The method is optimized such that only columns and rows that are of interest are parsed and read into R's memory. This minimizes memory usage at the same time as it speeds up the reading.

Keywords
IO
Usage
"readTable"(file, colClasses=NULL, isPatterns=FALSE, defColClass=NA, header=FALSE, skip=0, nrows=-1, rows=NULL, col.names=NULL, check.names=FALSE, path=NULL, ..., stripQuotes=TRUE, method=c("readLines", "intervals"), verbose=FALSE)
Arguments
file
A connection or a filename. If a filename, the path specified by path is added to the front of the filename. Unopened files are opened and closed at the end.
colClasses
Either a named or an unnamed character vector. If unnamed, it specified the column classes just as used by read.table. If it is a named vector, names(colClasses) are used to match the column names read (this requires that header=TRUE) and the column classes are set to the corresponding values.
isPatterns
If TRUE, the matching of names(colClasses) to the read column names is done by regular expressions matching.
defColClass
If the column class map specified by a named colClasses argument does not match some of the read column names, the column class is by default set to this class. The default is to read the columns in an "as is" way.
header
If TRUE, column names are read from the file.
skip
The number of lines (commented or non-commented) to skip before trying to read the header or alternatively the data table.
nrows
The number of rows to read of the data table. Ignored if rows is specified.
rows
An row index vector specifying which rows of the table to read, e.g. row one is the row following the header. Non-existing rows are ignored. Note that rows are returned in the same order they are requested and duplicated rows are also returned.
col.names
Same as in read.table().
check.names
Same as in read.table(), but default value is FALSE here.
path
If file is a filename, this path is added to it, otherwise ignored.
...
Arguments passed to read.table used internally.
stripQuotes
If TRUE, quotes are stripped from values before being parse. This argument is only effective when method=="readLines".
method
If "readLines", (readLines()) is used internally to first only read rows of interest, which is then passed to read.table(). If "intervals", contigous intervals are first identified in the rows of interest. These intervals are the read one by one using read.table(). The latter methods is faster and especially more memory efficient if the intervals are not too many, where as the former is prefered if many "scattered" rows are to be read.
verbose
A logical or a Verbose object.
Value

Returns a data.frame.

See Also

readTableIndex(). read.table. colClasses().

Aliases
  • readTable.default
  • readTable
Documentation reproduced from package R.utils, version 2.5.0, License: LGPL (>= 2.1)

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