A PolyData object comprises a data frame that summarises information
for each polyline/polygon in a PolySet; each PolyData record is defined by
PID or (
PBSmapping functions that expect PolyData will accept properly formatted data frames in their place (see 'Details').
as.PolyData attempts to coerce a data frame to an object with
TRUE if its argument is of class
data frame to be coerced or tested.
Boolean value; if
We define PolyData as a data frame with a first column named
and (optionally) a second column named
SID. Unlike a
PolySet, where each contour has many records corresponding
to the vertices, a PolyData object must have only one record for each
PID or each (
SID) combination. Conceptually,
this object associates data with contours, where the data correspond to
additional fields in the data frame. The R language conveniently
allows data frames to contain fields of various atomic modes
"null"). For example, PolyData with the
PName) might assign character names to a set
of primary polygons. Additionally, if fields
(perhaps representing locations for placing labels), consider adding
projection. Inserting the string
"PolyData" as the class attribute's first element alters the
behaviour of some functions, including
Our software particularly uses PolyData to set various plotting
characteristics. Consistent with graphical parameters used by the R/S
polygon, column names
can specify graphical properties:
lty - line type in drawing the border and/or shading
col - line or fill colour;
border - border colour;
density - density of shading lines;
angle - angle of shading lines.
When drawing polylines (as opposed to closed polygons), only
col have meaning.
as.PolyData method returns an object with classes
"data.frame", in that order.
Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
PolySet, EventData, LocationSet
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