write.dbf {foreign}R Documentation

Write a DBF File

Description

The function tries to write a data frame to a DBF file.

Usage

write.dbf(dataframe, file, factor2char = TRUE, max_nchar = 254)

Arguments

dataframe a data frame object.
file a file name to be written to.
factor2char logical, default TRUE, convert factor columns to character: otherwise they are written as the internal integer codes.
max_nchar The maximum number of characters allowed in a character field. Strings which exceed this will be truncated with a warning. See Details.

Details

Dots in column names are replaced by underlines in the DBF file, and names are truncated to 11 characters.

Only vector columns of classes "logical", "numeric", "integer", "character", "factor" and "Date" can be written. Other columns should be converted to one of these.

Maximum precision (number of digits including minus sign and decimal sign) for numeric is 19 - scale (digits after the decimal sign) which is calculated internally based on the number of digits before the decimal sign.

The original DBASE format limited character fields to 254 bytes. It is said that Clipper and FoxPro can read up to 32K, and it is possible to write a reader that could accept up to 65535 bytes. (The documentation suggests that only ASCII characters can be assumed to be supported.) Readers expecting the older standard (which includes Excel 2003, Access 2003 and OpenOffice 2.0) will truncate the field to the maximum width modulo 256, so increase max_nchar only if you are sure the intended reader supports wider character fields.

Value

Invisible NULL.

Note

Other applications have varying abilities to read the data types used here. Microsoft Access reads "numeric", "integer", "character" and "Date" fields, including recognizing missing values, but not "logical" (read as 0,-1). Microsoft Excel understood all possible types but did not interpret missing values in character fields correctly (showing them as character nuls).

Author(s)

Nicholas J. Lewin-Koh, modified by Roger Bivand and Brian Ripley; shapelib by Frank Warmerdam.

References

http://shapelib.maptools.org/

http://www.clicketyclick.dk/databases/xbase/format/data_types.html

See Also

read.dbf

Examples

str(warpbreaks)
try1 <- paste(tempfile(), ".dbf", sep = "")
write.dbf(warpbreaks, try1, factor2char = FALSE)
in1 <- read.dbf(try1)
str(in1)
try2 <- paste(tempfile(), ".dbf", sep = "")
write.dbf(warpbreaks, try2, factor2char = TRUE)
in2 <- read.dbf(try2)
str(in2)
unlink(c(try1, try2))

[Package foreign version 0.8-20 Index]