Read Fixed Width Format Files

Read a table of fixed width formatted data into a data.frame.

file, connection
read.fwf(file, widths, header = FALSE, sep = "\t",
         skip = 0, row.names, col.names, n = -1,
         buffersize = 2000, fileEncoding = "", …)

the name of the file which the data are to be read from.

Alternatively, file can be a connection, which will be opened if necessary, and if so closed at the end of the function call.


integer vector, giving the widths of the fixed-width fields (of one line), or list of integer vectors giving widths for multiline records.


a logical value indicating whether the file contains the names of the variables as its first line. If present, the names must be delimited by sep.


character; the separator used internally; should be a character that does not occur in the file (except in the header).


number of initial lines to skip; see read.table.


see read.table.


see read.table.


the maximum number of records (lines) to be read, defaulting to no limit.


Maximum number of lines to read at one time


character string: if non-empty declares the encoding used on a file (not a connection) so the character data can be re-encoded. See the ‘Encoding’ section of the help for file, the ‘R Data Import/Export Manual’ and ‘Note’.

further arguments to be passed to read.table. Useful such arguments include, na.strings, colClasses and strip.white.


Multiline records are concatenated to a single line before processing. Fields that are of zero-width or are wholly beyond the end of the line in file are replaced by NA.

Negative-width fields are used to indicate columns to be skipped, e.g., -5 to skip 5 columns. These fields are not seen by read.table and so should not be included in a col.names or colClasses argument (nor in the header line, if present).

Reducing the buffersize argument may reduce memory use when reading large files with long lines. Increasing buffersize may result in faster processing when enough memory is available.

Note that read.fwf (not read.table) reads the supplied file, so the latter's argument encoding will not be useful.


A data.frame as produced by read.table which is called internally.

See Also

scan and read.table.

read.fortran for another style of fixed-format files.

  • read.fwf
library(utils) ff <- tempfile() cat(file = ff, "123456", "987654", sep = "\n") read.fwf(ff, widths = c(1,2,3)) #> 1 23 456 \ 9 87 654 read.fwf(ff, widths = c(1,-2,3)) #> 1 456 \ 9 654 unlink(ff) cat(file = ff, "123", "987654", sep = "\n") read.fwf(ff, widths = c(1,0, 2,3)) #> 1 NA 23 NA \ 9 NA 87 654 unlink(ff) cat(file = ff, "123456", "987654", sep = "\n") read.fwf(ff, widths = list(c(1,0, 2,3), c(2,2,2))) #> 1 NA 23 456 98 76 54 unlink(ff)
Documentation reproduced from package utils, version 3.4.1, License: Part of R 3.4.1

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