Locate polygons on the current plot (using the locator
function).
locatePolys (pdata, n = 512, type = "o", …)PolyData (optional) with
columns PID and SID (optional), with two more
optional columns n and type.
maximum number of points to locate.
one of "n", "p", "l", or
"o". If "p" or "o", then the points are
plotted; if "l" or "o", then the points are joined by
lines.
PolySet with projection attribute equal to the map's
projection. The function does not set the zone attribute.
This function allows its user to define polygons with mouse clicks on
the current plot via the locator function. The
arguments n and type are the usual parameters for the
locator function, but the user can specify them for each
individual (PID, SID) in a pdata object.
If a pdata object exists, the function ignores columns other
than PID, SID, n, and type. If pdata
includes n, then an outer boundary has n > 0 and an
inner boundary has n < 0.
On exit from locator, suppose the user defined m
vertices for a given polygon. For that polygon, the X and
Y columns will contain NAs where POS =
(m+1):n for outer-boundaries and POS =
(|n|-m):1 for inner-boundaries. The
na.omit function can remove rows with NAs.
If a pdata object does not exist, the output contains only one
polygon with a PID equal to 1. One inner-boundary polygon
(POS goes from n to 1) can be generated by
supplying a negative n.
If type = "o" or type = "l", the function draws a line
connecting the last and first vertices.
addPolys,
appendPolys,
clipPolys,
closePolys,
findCells,
findPolys,
fixPOS,
joinPolys,
plotMap,
plotPolys,
thickenPolys,
thinPolys.
#--- define one polygon with up to 5 vertices on the current plot
polys <- locatePolys(n = 5)
Run the code above in your browser using DataLab