read.fwf {utils}R Documentation

Read Fixed Width Format Files


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


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


file 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.
widths integer vector, giving the widths of the fixed-width fields (of one line), or list of integer vectors giving widths for multiline records.
header 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.
sep character; the separator used internally; should be a character that does not occur in the file (except in the header). see read.table.
skip number of initial lines to skip; see read.table.
row.names see read.table.
col.names see read.table.
n the maximum number of records (lines) to be read, defaulting to no limit.
buffersize Maximum number of lines to read at one time
... further arguments to be passed to read.table. Useful further 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, eg -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.


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


Brian Ripley for R version: original Perl by Kurt Hornik.

See Also

scan and read.table.


ff <- tempfile()
cat(file=ff, "123456", "987654", sep="\n")
read.fwf(ff, width=c(1,2,3))    #> 1 23 456 \ 9 87 654
read.fwf(ff, width=c(1,-2,3))   #> 1 456 \ 9 654
cat(file=ff, "123", "987654", sep="\n")
read.fwf(ff, width=c(1,0, 2,3))    #> 1 NA 23 NA \ 9 NA 87 654
cat(file=ff, "123456", "987654", sep="\n")
read.fwf(ff, width=list(c(1,0, 2,3), c(2,2,2)))    #> 1 NA 23 456 98 76 54

[Package utils version 2.5.0 Index]