readTable
From R.utils v2.0.0
by Henrik Bengtsson
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
## S3 method for class 'default':
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 bypath
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 - isPatterns
- If
TRUE
, the matching ofnames(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 - col.names
- Same as in
read.table()
. - check.names
- Same as in
read.table()
, but default value isFALSE
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 whenmethod=="readLines"
. - method
- If
"readLines"
,(readLines())
is used internally to first only read rows of interest, which is then passed toread.table()
. If"intervals"
, contigous intervals are first identified in the - verbose
- A
logical
or aVerbose
object.
Value
- Returns a
data.frame
.
See Also
readTableIndex
().
read.table
.
colClasses
().
Community examples
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