read.table {base}R Documentation

Data Input

Description

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.

Usage

read.table(file, header = FALSE, sep = "", quote = "\"'", dec = ".",
           row.names, col.names, as.is = FALSE, na.strings = "NA",
           skip = 0, check.names = TRUE, fill = FALSE,
           strip.white = FALSE, blank.lines.skip = TRUE)

read.csv(file, header = TRUE, sep = ",", quote="\"", dec=".",
         fill = TRUE, ...)

read.csv2(file, header = TRUE, sep = ";", quote="\"", dec=",",
         fill = TRUE, ...)

read.delim(file, header = TRUE, sep = "\t", quote="\"", dec=".",
         fill = TRUE, ...)

read.delim2(file, header = TRUE, sep = "\t", quote="\"", dec=",",
         fill = TRUE, ...)

Arguments

file the name of the file which the data are to be read from. Each row of the table appears as one line of the file. If it does not contain an absolute path, the file name is relative to the current working directory, getwd(). Tilde-expansion is performed where supported.
Alternatively, file can be a connection, which will be opened if necessary, and if so closed at the end of the function call.
file can also be a complete URL.
header a logical value indicating whether the file contains the names of the variables as its first line. If missing, the value is determined from the file format: header is set to TRUE if and only if the first row contains one fewer field than the number of columns.
sep the field separator character. Values on each line of the file are separated by this character. If sep = "" (the default for read.table) the separator is ``white space'', that is one or more spaces, tabs or newlines.
quote the set of quoting characters. To disable quoting altogether, use quote="". See scan for the behaviour on quotes embedded in quotes.
dec the character used in the file for decimal points.
row.names a vector of row names. This can be a vector giving the actual row names, or a single number giving the column of the table which contains the row names, or character string giving the name of the table column containing the row names.
If there is a header and the first row contains one fewer field than the number of columns, the first column in the input is used for the row names. Otherwise if row.names is missing, the rows are numbered.
Using row.names = NULL forces row numbering.
col.names a vector of optional names for the variables. The default is to use "V" followed by the column number.
as.is the default behavior of read.table is to convert non-numeric variables to factors. The variable as.is controls this conversion. Its value is either a vector of logicals (values are recycled if necessary), or a vector of numeric indices which specify which columns should be left as character strings.
na.strings a vector strings which are to be interpreted as NA values.
skip the number of lines of the data file to skip before beginning to read data.
check.names logical. If TRUE then the names of the variables in the data frame are checked to ensure that they are syntactically valid variable names. If necessary they are adjusted (by make.names) so that they are.
fill logical. If TRUE then in case the rows have unequal length, blank fields are implicitly added.
strip.white logical. Used only when sep has been specified, and allows the stripping of leading and trailing white space from character fields (numeric fields are always stripped). See scan for further details, remembering that the columns may include the row names.
blank.lines.skip logical: if TRUE blank lines in the input are ignored.
... Further arguments to read.table.

Details

If row.names is not specified and the header line has one less entry than the number of columns, the first column is taken to be the row names. This allows data frames to be read in from the format in which they are printed. If row.names is specified and does not refer to the first column, that column is discarded from such files.

The number of data columns is determined by looking at the first five lines of input (or the whole file if it has less than five lines), or from the length of col.names if it is specified and is longer. This could conceivably be wrong if fill or blank.lines.skip are true.

read.csv and read.csv2 are identical to read.table except for the defaults. They are intended for reading ``comma separated value'' files (`.csv') or the variant used in countries that use a comma as decimal point and a semicolon as field separator. Similarly, read.delim and read.delim2 are for reading delimited files, defaulting to the TAB character for the delimiter. Notice that header = TRUE and fill = TRUE in these variants.

Value

A data frame (data.frame) containing a representation of the data in the file. Empty input is an error unless col.names is specified, when a 0-row data frame is returned: similarly giving just a header line if header = TRUE results in a 0-row data frame.
This function is the principal means of reading tabular data into R.

Note

The implementation of read.table currently reads everything as character using scan and subsequently defines "numeric" or factor variables.

This is quite memory consuming for files of thousands of records and may need larger memory, see Memory.

See Also

The `R Data Import/Export' manual.

scan, read.fwf for reading fixed width formatted input; read.table.url for ``reading'' data from the internet; write.table; data.frame.

count.fields can be useful to determine problems with reading files which result in reports of incorrect record lengths.