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"))



x the object to be written, preferably a matrix or data frame. If not, it is attempted to coerce x to a data frame.
file either a character string naming a file or a connection open for writing. "" indicates output to the console.
append logical. If TRUE, the output is appended to the file. If FALSE, any existing file of the name is destroyed.
quote 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.
sep the field separator string. Values within each row of x are separated by this string.
eol the character(s) to print at the end of each line (row).
na the string to use for missing values in the data.
dec the string to use for decimal points in numeric or complex columns: must be a single character.
row.names 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.
col.names 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.
qmethod a character string specifying how to deal with embedded double quote characters when quoting strings. Must be one of "escape" (default), in which case the quote character is escaped in C style by a backslash, or "double", in which case it is doubled. You can specify just the initial letter.
... arguments to write.table: 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 not open for writing, an attempt is made to open it and then close it after use.

CSV files

By default there is no 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.

write.csv and write.csv2 provide convenience wrappers for writing CSV files. They set sep, dec and qmethod, and col.names to NA if row.names = TRUE and 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 col.names, sep, dec or qmethod are ignored, with a warning.


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.


## Not run: 
## To write a CSV file for input to Excel one might use
x <- data.frame(a = I("a \" quote"), b = pi)
write.table(x, file = "foo.csv", sep = ",", col.names = NA,
            qmethod = "double")
## and to read this file back into R one needs
read.table("foo.csv", header = TRUE, sep = ",", row.names = 1)
## NB: you do need to specify a separator if qmethod = "double".

### Alternatively
write.csv(x, file = "foo.csv")
read.csv("foo.csv", row.names = 1)
## or without row names
write.csv(x, file = "foo.csv", row.names = FALSE)
## End(Not run)

[Package utils version 2.5.0 Index]