| clipPolys {PBSmapping} | R Documentation |
Clips a PolySet, where each unique (PID, SID) describes
a polygon.
clipPolys (polys, xlim, ylim, keepExtra = FALSE)
polys |
PolySet to clip. |
xlim |
range of X-coordinates. |
ylim |
range of Y-coordinates. |
keepExtra |
Boolean value; if TRUE, tries to
carry forward any non-standard columns into the result. |
For each discrete polygon, the function connects vertices 1 and N. It
recalculates the POS values for each vertex, saving the old
values in a column named oldPOS. For new vertices, it sets
oldPOS to NA.
PolySet containing the input data, with some points added or
removed. A new column oldPOS records the original POS
value for each vertex.
#--- create a triangle that will be clipped
polys <- data.frame(PID=rep(1, 3), POS=1:3, X=c(0,1,.5), Y=c(0,0,1))
#--- clip the triangle in the X direction, and plot the results
plotPolys(clipPolys(polys, xlim=c(0,.75), ylim=range(polys[, "Y"])),
col=2);