centroid.owin
Centroid of a window
Computes the centroid (centre of mass) of a window
Usage
centroid.owin(w, as.ppp = FALSE)Arguments
- w
A window
- as.ppp
Logical flag indicating whether to return the centroid as a point pattern (
pppobject)
Details
The centroid of the window w is computed.
The centroid (``centre of mass'')
is the point whose \(x\) and \(y\) coordinates
are the mean values of the \(x\) and \(y\) coordinates
of all points in the window.
The argument w should be a window (an object of class
"owin", see owin.object for details)
or can be given in any format acceptable to as.owin().
The calculation uses an exact analytic formula for the case of polygonal windows.
Note that the centroid of a window is not necessarily inside
the window, unless the window is convex.
If as.ppp=TRUE and
the centroid of w lies outside w,
then the window of the returned point pattern
will be a rectangle containing the
original window (using as.rectangle.
Value
Either a list with components x, y, or a point pattern (of class
ppp) consisting of a single point, giving the coordinates of the
centroid of the window w.
See Also
Examples
# NOT RUN {
w <- owin(c(0,1),c(0,1))
centroid.owin(w)
# returns 0.5, 0.5
data(demopat)
w <- Window(demopat)
# an irregular window
cent <- centroid.owin(w, as.ppp = TRUE)
# }
# NOT RUN {
plot(cent)
# plot the window and its centroid
# }
# NOT RUN {
wapprox <- as.mask(w)
# pixel approximation of window
# }
# NOT RUN {
points(centroid.owin(wapprox))
# should be indistinguishable
# }
# NOT RUN {
# }