Calculate an n-by-n matrix by applying a function to all pairs of columns of an m-by-n matrix.
Calculate an n-by-n matrix by applying a function to all pairs of columns of an m-by-n matrix.
dist2(x, fun, diagonal=0)
x |
A matrix. |
fun |
A symmetric function of two arguments that may be columns of |
diagonal |
The value to be used for the diagonal elements of the resulting matrix. |
With the default value of fun, this function calculates
for each pair of columns of x the mean of the absolute values
of their differences (which is proportional to the L1-norm of their
difference). This is a distance metric.
The implementation assumes that
fun(x[,i], x[,j]) can be evaluated for all pairs of i
and j (see examples), and that
fun is symmetric, i.e.
fun(a, b) = fun(b, a).
fun(a, a) is not actually evaluated, instead the value of diagonal
is used to fill the diagonal elements of the returned matrix.
Note that dist computes distances between rows of
x, while this function computes relations between columns of
x (see examples).
A symmetric matrix of size n x n.
Wolfgang Huber, James Reid
# example matrix
z = matrix(1:15693, ncol=3)
matL1 = dist2(z)
matL2 = dist2(z, fun=function(a,b) sqrt(sum((a-b)^2, na.rm=TRUE)))
euc = as.matrix(dist(t(z)))
stopifnot(identical(dim(matL2), dim(euc)),
all(euc==matL2))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.