subset.dist {cba}R Documentation

Subsetting Compact Symmetric Matrices

Description

This function conveniently returns a subset (submatrix) of an object of class dist.

Usage

## S3 method for class 'dist':
subset(x, subset, ...)
## S3 method for class 'dist':
x[[subset, ...]]

x[[i]]

Arguments

x an object of class dist
subset, i logical, character, or index vector
... other (unused) arguments

Details

For consistency, subsetting a symmetric matrix is constrained to a single index (vector). However, non-unique indexing is allowed. In this case zero is returned for diagonal elements.

If x has a Labels attribute a character vector can be used for subsetting.

Note that objects which contain diagonal elements are not handled.

Value

An object of class dist.

Warning

This is experimental code which may change in future releases.

Author(s)

Christian Buchta

See Also

dist for details

Examples

x <- as.dist(matrix(1:36, ncol=6))
subset(x, c(2,4,6))
subset(x, c(4,2,6))               # same set but different order
attr(x, "Labels") <- letters[1:6] # hack!
subset(x, c(2,4,6))
subset(x, letters[c(2,4,6)])
subset(x, c(2,2,4,6))             # contains one zero 
# this is more user friendly
x[[c(2,4,6)]]
x[[c("b","d","e")]]

[Package cba version 0.1-8 Index]