| write.polylistShape {maptools} | R Documentation |
The function calls code from shapelib to write a polygon-type shapefile from an S3 polylist object.
write.polylistShape(polylist, df, file, factor2char = TRUE, strictFilename=FALSE, force = FALSE)
polylist |
list of polygons of class polylist |
df |
a data frame object |
file |
a file name of maximum 8 chararacters, numbers or the underscore symbol to be written, omitting the extensions *.shp, *.shx and *.dbf, which are added in the function |
factor2char |
logical, default TRUE, convert factor columns to character |
strictFilename |
if TRUE, impose file basename length limit of 8 characters |
force |
default FALSE, can be set to TRUE to try to force malformed polylist objects to some reasonable form that will not cause both maptools and R to crash. Because polylist objects are old-style rather than new-style classes, it is possible to crash R by trying to write malformed objects. Attempts are made to check for known problems, but using polylist objects rather than sp SpatialPolygons objects is known to be more risky. |
The function calls code from shapelib to write a polygon-type shapefile (both the geometry file with a *.shp extension, the index file with a *.shx extension, and the database file with a *.dbf extension - see write.dbf for details of the data frame export within this function.
no return value.
From maptools 0.4-7, this function is placed in the user-visible namespace on a trial basis, and reports of any malfunction should be sent to the package maintainer, Roger Bivand Roger.Bivand@nhh.no. It is likely that this function and its arguments will be changed.
Nicholas J. Lewin-Koh, modified by Roger Bivand; shapelib by Frank Warmerdam
col_orig <- read.shape(system.file("shapes/columbus.shp", package="maptools")[1])
mappolys <- Map2poly(col_orig, as.character(col_orig$att.data$NEIGNO))
plot(mappolys)
col_df <- col_orig$att.data
col_cheap <- subset(mappolys, col_df$HOVAL < 34)
col_df_cheap <- subset(col_df, col_df$HOVAL < 34)
file <- tempfile("")
write.polylistShape(col_cheap, col_df_cheap, file)
getinfo.shape(paste(file, ".shp", sep=""))
col_new <- read.shape(paste(file, ".shp", sep=""))
mappolys <- Map2poly(col_new, as.character(col_new$att.data$NEIGNO))
plot(mappolys, border="red", add=TRUE)