write.fwf writes object in *f*ixed *w*idth *f*ormat.write.fwf(x, file="", append=FALSE, quote=FALSE, sep=" ", na="",
rownames=FALSE, colnames=TRUE, rowCol=NULL, justify="left",
formatInfo=FALSE, quoteInfo=TRUE, width=NULL, eol="",
qmethod=c("escape", "double"), ...) - x
{data.frame or matrix, the object to be written}
- file
{character, name of file or connection, look in
write.table for more}
- append
{logical, append to existing data in file}
- quote
{logical, quote data in output}
- na
{character, the string to use for missing values
i.e. NA in the output}
- sep
{character, separator between columns in output}
- rownames
{logical, print row names}
- colnames
{logical, print column names}
- rowCol
{character, rownames column name}
- justify
{character, alignment of character columns; see
format}
- formatInfo
{logical, return information on number of levels,
widths and format}
- quoteInfo
{logical, should formatInfo account for quotes}
- width
{numeric, width of the columns in the output}
- eol
{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 Mac
OS Excel 2004.}
- 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.}
- ...
{further arguments to
format.info and format
}
*F*ixed *w*idth *f*ormat is not used widely anymore. Use some other
format (say *c*omma *s*eparated *v*alues; see read.csv) if
you can. However, if you need fixed width format then write.fwf
can help you.
Output is similar to print(x) or format(x). Formatting is
done completely by format on a column basis. Columns in
the output are by default separated with a space i.e. empty column with
a width of one character, but that can be changed with sep
argument as passed to write.table via ....
As mentioned formatting is done completely by
format. Arguments can be passed to format via
... to further modify the output. However, note that the
returned formatInfo might not properly account for this, since
format.info (which is used to collect information about
formatting) lacks the arguments of format.
quote can be used to quote fields in the output. Since all
columns of x are converted to character (via
format) during the output, all columns will be quoted! If
quotes are used, read.table can be easily used to read the
data back into R. Check examples. Do read the details about
quoteInfo argument.
Use only *true* character, i.e., avoid use of tabs, i.e., "\t", or similar
separators via argument sep. Width of the separator is taken as
the number of characters evaluated via nchar(sep).
Use argument na to convert missing/unknown values. Only single value
can be specified. Use NAToUnknown prior to export if you need
greater flexibility.
If rowCol is not NULL and rownames=TRUE, rownames
will also have column name with rowCol value. This is mainly for
flexibility with tools outside R. Note that (at least in R2.4.0) it
is not "easy" to import data back to Rwith read.fwf if
you also export rownames. This is the reason, that default is
rownames=FALSE.
Information about format of output will be returned if
formatInfo=TRUE. Returned value is described in value
section. This information is gathered by format.info and
care was taken to handle numeric properly. If output contains rownames,
values account for this. Additionally, if rowCol is not
NULL returned values contain also information about format
of rownames.
If quote=TRUE, the output is of course wider due to
quotes. Return value (with formatInfo=TRUE) can account for this
in two ways; controlled with argument quoteInfo. However, note
that there is no way to properly read the data back to Rif
quote=TRUE & quoteInfo=FALSE arguments were used for
export. quoteInfo applies only when quote=TRUE. Assume
that there is a file with quoted data as shown bellow (column numbers in
first three lines are only for demonstration of the values in the
output).
123456789 12345678 # for position
123 1234567 123456 # for width with quoteInfo=TRUE
1 12345 1234 # for width with quoteInfo=FALSE
"a" "hsgdh" " 9"
" " " bb" " 123"
With quoteInfo=TRUE write.fwf will return
colname position width
V1 1 3
V2 5 7
V3 13 6
or (with quoteInfo=FALSE)
colname position width
V1 2 1
V2 6 5
V3 14 4
Argument width can be used to increase the width of the columns
in the output. This argument is passed to the width argument of
format function. Values in width are recycled if
there is less values than the number of columns. If the specified width
is to short in comparison to the "width" of the data in particular
column, error is issued.
Besides its effect to write/export data write.fwf can provide
information on format and width. A data.frame is returned with the
following columns:
- colname
{name of the column}
- nlevels
{number of unique values (unused levels of factors are
dropped), 0 for numeric column}
- position
{starting column number in the output}
- width
{width of the column}
- digits
{number of digits after the decimal point}
- exp
{width of exponent in exponential representation; 0 means
there is no exponential representation, while 1 represents exponent
of length one i.e. 1e+6 and 2 1e+06 or 1e+16}
[object Object]
format.info, format,
NAToUnknown, write.table,
read.fwf, read.table and
trim
## Some data
num <- round(c(733070.345678, 1214213.78765456, 553823.798765678,
1085022.8876545678, 571063.88765456, 606718.3876545678,
1053686.6, 971024.187656, 631193.398765456, 879431.1),
digits=3)
testData <- data.frame(num1=c(1:10, NA),
num2=c(NA, seq(from=1, to=5.5, by=0.5)),
num3=c(NA, num),
int1=c(as.integer(1:4), NA, as.integer(4:9)),
fac1=factor(c(NA, letters[1:9], "hjh")),
fac2=factor(c(letters[6:15], NA)),
cha1=c(letters[17:26], NA),
cha2=c(NA, "longer", letters[25:17]),
stringsAsFactors=FALSE)
levels(testData$fac1) <- c(levels(testData$fac1), "unusedLevel")
testData$Date <- as.Date("1900-1-1")
testData$Date[2] <- NA
testData$POSIXt <- as.POSIXct(strptime("1900-1-1 01:01:01",
format="%Y-%m-%d %H:%M:%S"))
testData$POSIXt[5] <- NA
## Default
write.fwf(x=testData)
## NA should be -
write.fwf(x=testData, na="-")
## NA should be -NA-
write.fwf(x=testData, na="-NA-")
## Some other separator than space
write.fwf(x=testData[, 1:4], sep="-mySep-")
## Force wider columns
write.fwf(x=testData[, 1:5], width=20)
## Write to file and report format and fixed width information
file <- tempfile()
formatInfo <- write.fwf(x=testData, file=file, formatInfo=TRUE)
## Read exported data back to R (note +1 due to separator)
## ... without header
read.fwf(file=file, widths=formatInfo$width + 1, header=FALSE, skip=1,
strip.white=TRUE)
## ... with header - via postimport modfication
tmp <- read.fwf(file=file, widths=formatInfo$width + 1, skip=1,
strip.white=TRUE)
colnames(tmp) <- read.table(file=file, nrow=1, as.is=TRUE)
tmp
## ... with header - persuading read.fwf to accept header properly
## (thanks to Marc Schwartz)
read.fwf(file=file, widths=formatInfo$width + 1, strip.white=TRUE,
skip=1, col.names=read.table(file=file, nrow=1, as.is=TRUE))
## ... with header - with the use of quotes
write.fwf(x=testData, file=file, quote=TRUE)
read.table(file=file, header=TRUE, strip.white=TRUE)
## Tidy up
unlink(file)
print
file