write.table {utils}R Documentation

Data Output


write.table prints its required argument x (after converting it to a data frame if it is not one nor a matrix) to a file or connection.


write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ",
            eol = "\n", na = "NA", dec = ".", row.names = TRUE,
            col.names = TRUE, qmethod = c("escape", "double"),
            fileEncoding = "")




the object to be written, preferably a matrix or data frame. If not, it is attempted to coerce x to a data frame.


either a character string naming a file or a connection open for writing. "" indicates output to the console.


logical. Only relevant if file is a character string. If TRUE, the output is appended to the file. If FALSE, any existing file of the name is destroyed.


a logical value (TRUE or FALSE) or a numeric vector. If TRUE, any character or factor columns will be surrounded by double quotes. If a numeric vector, its elements are taken as the indices of columns to quote. In both cases, row and column names are quoted if they are written. If FALSE, nothing is quoted.


the field separator string. Values within each row of x are separated by this string.


the character(s) to print at the end of each line (row). For example, eol = "\r\n" will produce Windows' line endings on a Unix-alike OS, and eol = "\r" will produce files as expected by Excel:mac 2004.


the string to use for missing values in the data.


the string to use for decimal points in numeric or complex columns: must be a single character.


either a logical value indicating whether the row names of x are to be written along with x, or a character vector of row names to be written.


either a logical value indicating whether the column names of x are to be written along with x, or a character vector of column names to be written. See the section on ‘CSV files’ for the meaning of col.names = NA.


a character string specifying how to deal with embedded double quote characters when quoting strings. Must be one of "escape" (default for write.table), in which case the quote character is escaped in C style by a backslash, or "double" (default for write.csv and write.csv2), in which case it is doubled. You can specify just the initial letter.


character string: if non-empty declares the encoding to be used on a file (not a connection) so the character data can be re-encoded as they are written. See file.


arguments to write.table: append, col.names, sep, dec and qmethod cannot be altered.


If the table has no columns the rownames will be written only if row.names = TRUE, and vice versa.

Real and complex numbers are written to the maximal possible precision.

If a data frame has matrix-like columns these will be converted to multiple columns in the result (via as.matrix) and so a character col.names or a numeric quote should refer to the columns in the result, not the input. Such matrix-like columns are unquoted by default.

Any columns in a data frame which are lists or have a class (e.g., dates) will be converted by the appropriate as.character method: such columns are unquoted by default. On the other hand, any class information for a matrix is discarded and non-atomic (e.g., list) matrices are coerced to character.

Only columns which have been converted to character will be quoted if specified by quote.

The dec argument only applies to columns that are not subject to conversion to character because they have a class or are part of a matrix-like column (or matrix), in particular to columns protected by I(). Use options("OutDec") to control such conversions.

In almost all cases the conversion of numeric quantities is governed by the option "scipen" (see options), but with the internal equivalent of digits = 15. For finer control, use format to make a character matrix/data frame, and call write.table on that.

These functions check for a user interrupt every 1000 lines of output.

If file is a non-open connection, an attempt is made to open it and then close it after use.

To write a Unix-style file on Windows, use a binary connection e.g. file = file("filename", "wb").

CSV files

By default, write.table does not output a column name for a column of row names. If col.names = NA and row.names = TRUE a blank column name is added, which is the convention used for CSV files to be read by spreadsheets. Note that such CSV files can be read in R by

  read.csv(file = "<filename>", row.names = 1)

write.csv and write.csv2 provide convenience wrappers for writing CSV files. They set sep and dec (see below), qmethod = "double", and col.names to NA if row.names = TRUE (the default) and to TRUE otherwise.

write.csv uses "." for the decimal point and a comma for the separator.

write.csv2 uses a comma for the decimal point and a semicolon for the separator, the Excel convention for CSV files in some Western European locales.

These wrappers are deliberately inflexible: they are designed to ensure that the correct conventions are used to write a valid file. Attempts to change append, col.names, sep, dec or qmethod are ignored, with a warning.

CSV files do not record an encoding, and this causes problems if they are not ASCII for many other applications. Windows Excel 2007/10 will open files (e.g., by the file association mechanism) correctly if they are ASCII or UTF-16 (use fileEncoding = "UTF-16LE") or perhaps in the current Windows codepage (e.g., "CP1252"), but the ‘Text Import Wizard’ (from the ‘Data’ tab) allows far more choice of encodings. Excel:mac 2004/8 can import only ‘Macintosh’ (which seems to mean Mac Roman), ‘Windows’ (perhaps Latin-1) and ‘PC-8’ files. OpenOffice 3.x asks for the character set when opening the file.

There is an IETF RFC4180 (https://www.rfc-editor.org/rfc/rfc4180) for CSV files, which mandates comma as the separator and CRLF line endings. write.csv writes compliant files on Windows: use eol = "\r\n" on other platforms.


write.table can be slow for data frames with large numbers (hundreds or more) of columns: this is inevitable as each column could be of a different class and so must be handled separately. If they are all of the same class, consider using a matrix instead.

See Also

The ‘R Data Import/Export’ manual.

read.table, write.

write.matrix in package MASS.


x <- data.frame(a = I("a \" quote"), b = pi)
tf <- tempfile(fileext = ".csv")

## To write a CSV file for input to Excel one might use
write.table(x, file = tf, sep = ",", col.names = NA,
            qmethod = "double")
## and to read this file back into R one needs
read.table(tf, header = TRUE, sep = ",", row.names = 1)
## NB: you do need to specify a separator if qmethod = "double".

### Alternatively
write.csv(x, file = tf)
read.csv(tf, row.names = 1)
## or without row names
write.csv(x, file = tf, row.names = FALSE)

## Not run: 
## To write a file in Mac Roman for simple use in Mac Excel 2004/8
write.csv(x, file = "foo.csv", fileEncoding = "macroman")
## or for Windows Excel 2007/10
write.csv(x, file = "foo.csv", fileEncoding = "UTF-16LE")

## End(Not run)

[Package utils version 4.5.0 Index]