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 (
ppp
object)
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 {
# }