shapefiles

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Read and write ESRI shapefiles

This package includes functions to read and write ESRI shapefiles.

Keywords
programming
Usage
read.shapefile(shape.name)
read.shp(shp.name)
read.shx(shx.name) 
read.dbf(dbf.name) 
write.shapefile(shapefile, out.name)
write.shp(shp, out.name)
write.shx(shx, out.name)
write.dbf(dbf, out.name)
calc.header(shapefile)
add.xy(shapefile)
scaleXY(shapefile, scale.factor)
emme2.shp(nodes, links, file.name="d211.in")
Arguments
shape.name
String of the shapefile file name without an extension
shp.name
String of the shp file name with an extension
shx.name
String of the shx file name with an extension
dbf.name
String of the dbf file name with an extension
shapefile
The shapefile object of lists created by read.shapefile
out.name
Filename to write the data to
shp
shp portion (list) of the shapefile object of lists
shx
shx portion (list) of the shapefile object of lists
dbf
dbf portion (list) of the shapefile object of lists
scale.factor
Number to divide the shapefile geography by
nodes
Points shapefile object of lists
links
Lines shapefile object of lists
file.name
String of EMME/2 d211 import file to save to
Details

ESRI shapefiles consist of three files. The first file (*.shp) contains the geography of each shape. The second file (*.shx) is an index file which contains record offsets. The third file (*.dbf) contains feature attributes with one record per feature. read.shapefile calls read.shp, read.shx, and read.dbf to read in an entire shapefile. The result of read.shapefile is a list of many more lists. The sublists are shp, shx, and dbf. Each sublist contains a header list and some sort of data list. The shp list is a list of $shp$header and $shp$shp. The shx list is a list of $shx$header and $shx$index. The dbf list is a list of $dbf$header and $dbf$dbf. Currently only the read functions are really that useful. The write functions work fine, but building the necessary data in R to write out all the appropriate data in the shp and dbf files is absent at this point. For details about the ESRI shapefile structure refer to http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf. A detailed description of DBF files can be found at http://www.e-bachmann.dk/docs/xbase.htm. Note that the RODBC package function odbcConnectDbase is faster than read.dbf.

Value

  • lll{ read.shapefile list shapefile list object read.shp list shp list object read.shx list shx list object read.dbf list DBF list object write.shapefile NA Nothing returned write.shp NA Nothing returned write.shx NA Nothing returned write.dbf NA Nothing returned calc.header list shapefile list object add.xy list shapefile list object scaleXY list shapefile list object emme2.shp NA Nothing returned }

Aliases
  • read.shapefile
  • read.shp
  • read.shx
  • read.dbf
  • write.shapefile
  • write.shp
  • write.shx
  • write.dbf
  • calc.header
  • add.xy
  • scaleXY
  • emme2.shp
Examples
#Read entire shapefile
shapefile <- read.shapefile("links")

#Write entire shapefile
write.shapefile(shapefile, "temp")

#Read shp, shx, or dbf file
dbf <- read.dbf("links.dbf")

#Write shp, shx, or dbf file
write.dbf(dbf, "links.dbf")

#Calculate header (to clean up GeoMedia shapefile exports)
shapefile <- calc.header(shapefile)

#Add the X and Y coordinates to the dbf list of the shapefile list object
shapefile <- add.xy(shapefile)

#Scale the shapefile by scale.factor
shapefile <- scaleXY(shapefile, scale.factor)

#Create an EMME/2 network batch-in file
emme2.shp(nodes, links, "d211.in")
Documentation reproduced from package shapefiles, version 0.1, License: GPL

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