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 i
th entry is the distance
from the i
th point of X
to the nearest point of
Y
). The second column gives the indices of the nearest
neighbours (i.e. the i
th 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)