Import an ESRI shapefile (.shp) into either a
PolySet or EventData.
importShapefile (fn, readDBF=TRUE, projection=NULL, zone=NULL,
minverts=3, placeholes=FALSE, show.progress=FALSE)character -- file name of the shapefile to import; specifying the
extension is optional.
logical -- if TRUE, import the associated
".dbf" (database containing feature attributes) and add as an attribute
to the output PolySet | EventData object.
character -- optional projection attribute to override the
internally derived value.
numeric -- optional zone attribute to override the default
value of NULL.
numeric -- minimum number of vertices required for a polygon
representing a hole to be retained (does not affect solids).
logical -- if TRUE then for every PID
identify solids and holes, and place holes under appropriate solids.
logical -- if TRUE, display on the
command console the progress of placing holes under solids.
For points, EventData with columns EID, X, and
Y, possibly with other columns from the attribute database. For
polylines and polygons, a PolySet with columns PID,
SID, POS, X, Y and attribute projection.
Other attributes that may or may not be attached: parent.child
(boolean vector from original input), shpType (numeric shape
type: 1, 3, or 5), prj (projection information from .prj
file, xml (metadata from an .xml file), PolyData
(data from the attribute database .dbf), and zone (UTM zone).
This routine imports an ESRI shapefile (.shp) into either a
PolySet or EventData, depending on the type of
shapefile. It supports types 1 (Point), 3 (PolyLine), and 5 (Polygon)
and imports type 1 into EventData and types 3 and 5 into a
PolySet. In addition to the shapefile (.shp), it
requires the related index file (.shx).
If a database containing feature attributes (.dbf) exists, it
also imports this database by default. For EventData, it binds
the database columns to the EventData object. For a
PolySet, it saves the database in a PolyData object and
attaches that object to the PolySet in an attribute named
“PolyData”.
If a .prj file exists, this information is attached as an attribute.
If the first 3 characters are ‘GEO’, then a geographic projection
is assumed and projection="LL". If the first 4 characters are
‘PROJ’, and ‘UTM’ occurs elsewhere in the string, then the
Universal Transverse Mercator projection is assumed and projection="UTM".
Otherwise, projection=1.
If an .xml file exists, this information is attached as an attribute.
Shapes of numeric shape type 5 exported from ArcView in geographic
projection identify solids as polygons with vertices following a clockwise
path and holes as polygons that follow a counter-clockwise path.
Unfortuantely, either the export from ArcView or the import using a C-routine
from the package maptools often does not report solids followed by their holes.
We employ a new R function placeHoles to do this for us.
Ideally, this routine should be rendered in C, but for now we use this
function if the user sets the argument placeholes=TRUE.
Depending on the size and complexity of your shapefile, the computation may take a while.
importGSHHS,
importEvents,
importLocs,
importPolys,
placeHoles