write.fwf: Write object in fixed width format

Description

write.fwf writes object in *f*ixed *w*idth *f*ormat.

Usage

write.fwf(x, file="", append=FALSE, quote=FALSE, sep=" ", na="",
  rownames=FALSE, colnames=TRUE, rowCol=NULL, justify="right",
  formatInfo=FALSE, quoteInfo=TRUE, ...)

Arguments

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

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, allignment of character columns

formatInfo

logical, return information on number of levels, widths and format

quoteInfo

logical, should formatInfo account for quotes

...

further arguments to format.info, format and write.table

concept

data output
data export

Details

Output is similar to print(x) or format(x). Formating 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 ....

quote can be used to quote fields in the output. Since all columns of x are converted to character during the output, all columns will be quoted! The following is needed for read.fwf or any other tools outside R. If quotes are used, read.table can be easily used to read the data back into R. Check examples. Do read details on quoteInfo.

Use only *true* character i.e. not "" or similar for sep as number of characters in sep is needed internally.

Use na to convert missing/unknown values. Only single value can be specified. Take a look at NAToUnknown 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. That is the reason, that default is rownames=FALSE.

Information about format of output can be returned if formatInfo=TRUE. Returned value is described in value section. Result is provided by format.info and care was taken to handle numeric properly. If output contains rownames, returned value accounts for this. Additionally, if rowCol is not NULL then returned value contains also information about format of rownames.

If quote=TRUE output is 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 data back to Rif quote=TRUE & quoteInfo=FALSE was specifed for export. quoteInfo applies only when quote=TRUE. Assume there is a file with quoted data as shown bellow (column numbers in first three line 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 (symbolically)

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

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 testData <- data.frame(num1=c(1:10, NA), num2=c(NA, seq(from=1, to=5.5, by=0.5)), num3=c(NA, rnorm(n=10, mean=1e6, sd=3e5)), int1=c(as.integer(1:4), NA, as.integer(5:10)), fac1=factor(c(NA, letters[1:10])), fac2=factor(c(letters[6:15], NA)), cha1=c(letters[17:26], NA), cha2=c(NA, letters[26:17]), 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 - or ------------ write.fwf(x=testData, na="-") write.fwf(x=testData, na="------------")

## Some other separator than space write.fwf(x=testData[, 1:4], sep="-mySep-")

## Write to file and report format and fixed width information file <- tempfile("test.txt") 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