| nncross {spatstat} | R Documentation |
Given two point patterns X and Y,
finds the nearest neighbour in Y of each point of X.
nncross(X, Y)
X, Y |
Two point patterns (objects of class "ppp"). |
Given two point patterns X and Y this
function finds, for each point of X, the
the nearest point of Y. The distance between these points
is also computed.
The return value is a data frame, with rows corresponding to
the points of X. The first column gives the nearest neighbour
distances (i.e. the ith entry is the distance
from the ith point of X to the nearest point of
Y). The second column gives the indices of the nearest
neighbours (i.e. the ith entry is the index of
the nearest point in Y.)
Note that this function is not symmetric in X and Y.
To find the nearest neighbour in X of each point in Y,
just use nncross(Y,X).
A data frame with two columns:
dist |
Nearest neighbour distance |
which |
Nearest neighbour index in Y |
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
X <- runifpoint(15)
Y <- runifpoint(20)
N <- nncross(X,Y)$which
# note that length(N) = 15
plot(superimpose(X=X,Y=Y), main="nncross", cols=c("red","blue"))
arrows(X$x, X$y, Y[N]$x, Y[N]$y, length=0.15)