Move Point To Nearest Line
Given a point pattern and a line segment pattern, this function moves each point to the closest location on a line segment.
project2segment(X, Y)
X |
A point pattern (object of class |
Y |
A line segment pattern (object of class |
For each point x in the point pattern X, this function
finds the closest line segment y in the line segment pattern
Y. It then ‘projects’ the point x onto the line segment
y by finding the position z along y
which is closest to x. This position z is returned,
along with supplementary information.
A list with the following components. Each component has length equal to
the number of points in X, and its entries correspond to the
points of X.
Xproj |
Point pattern (object of class |
mapXY |
Integer vector identifying the nearest segment to each point. |
d |
Numeric vector of distances from each point of |
tp |
Numeric vector giving the scaled parametric coordinate 0 <= tp <= 1 of the position of the projected point along the segment. |
For example suppose mapXY[2] = 5 and tp[2] = 0.33.
Then Y[5] is the line segment lying closest to X[2].
The projection of the point X[2] onto the segment Y[5]
is the point Xproj[2], which lies one-third of the way
between the first and second endpoints of the line segment Y[5].
Adrian Baddeley Adrian.Baddeley@curtin.edu.au
and Rolf Turner r.turner@auckland.ac.nz
nearestsegment for a faster way to determine
which segment is closest to each point.
X <- rsyst(square(1), nx=5) Y <- as.psp(matrix(runif(20), 5, 4), window=owin()) plot(Y, lwd=3, col="green") plot(X, add=TRUE, col="red", pch=16) v <- project2segment(X,Y) Xproj <- v$Xproj plot(Xproj, add=TRUE, pch=16) arrows(X$x, X$y, Xproj$x, Xproj$y, angle=10, length=0.15, col="red")
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