| dist {mva} | R Documentation |
Distance Matrix Computation
Description
This function computes and returns the distance matrix computed by using the specified distance measure to compute the distances between the rows of a data matrix.
Usage
dist(x, method = "euclidean", diag = FALSE, upper = FALSE)
print.dist(x, diag = NULL, upper = NULL, ...)
as.matrix.dist(x)
as.dist(m, diag = FALSE, upper = FALSE)
Arguments
x |
A matrix or (data frame). Distances between the rows of
|
method |
The distance measure to be used. This must be one of
|
diag |
A logical value indicating whether the diagonal of the
distance matrix should be printed by |
upper |
A logical value indicating whether the upper triangle of the
distance matrix should be printed by |
m |
A matrix of distances to be converted to a |
... |
further arguments, passed to the (next) |
Details
Available distance measures are (written for two vectors x and
y):
euclidean:Usual square distance between the two vectors (2 norm).
maximum:Maximum distance between two components of
xandy(supremum norm)manhattan:Absolute distance between the two vectors (1 norm).
canberra:\sum_i |x_i - y_i| / |x_i + y_i|. Terms with zero numerator and denominator are omitted from the sum and treated as if the values were missing.binary:(aka asymmetric binary): The vectors are regarded as binary bits, so non-zero elements are ‘on’ and zero elements are ‘off’. The distance is the proportion of bits in which only one is on amongst those in which at least one is on.
Missing values are allowed, and are excluded from all computations
involving the rows within which they occur. If some columns are
excluded in calculating a Euclidean, Manhattan or Canberra distance,
the sum is scaled up proportionally to the number of columns used.
If all pairs are excluded when calculating a particular distance,
the value is NA.
The functions as.matrix.dist() and as.dist() can be used
for conversion between objects of class "dist" and conventional
distance matrices and vice versa.
Value
An object of class "dist".
The lower triangle of the distance matrix stored by columns in a
single vector. The vector has the attributes "Size",
"Diag", "Upper", "Labels" and "class" equal
to "dist".
References
Mardia, K. V., Kent, J. T. and Bibby, J. M. (1979) Multivariate Analysis. London: Academic Press.
See Also
hclust.
Examples
x <- matrix(rnorm(100), nrow=5)
dist(x)
dist(x, diag = TRUE)
dist(x, upper = TRUE)
m <- as.matrix(dist(x))
d <- as.dist(m)
stopifnot(d == dist(x))
names(d) <- LETTERS[1:5]
print(d, digits = 3)
## example of binary and canberra distances.
x <- c(0, 0, 1, 1, 1, 1)
y <- c(1, 0, 1, 1, 0, 1)
dist(rbind(x,y), method="binary")
## answer 0.4 = 2/5
dist(rbind(x,y), method="canberra")
## answer 2 * (6/5)