| subset.dist {cba} | R Documentation |
This function conveniently returns a subset (submatrix) of a sparse symmetric (distance) matrix.
## S3 method for class 'dist': subset(x, subset, ...) ## S3 method for class 'dist': x[[subset, ...]] x[[i]]
x |
an object of class dist. |
subset, i |
logical, character, or index vector. |
... |
further (unused) arguments. |
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 an error is raised if subset contains NA,
or a non-finite value.
An object of class dist.
This is experimental code which may change in future releases.
Christian Buchta
dist for details.
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")]]
## finally, don't use NA, etc.
z <- try(x[[c(2,NA,6)]], silent=TRUE)
z