spam (version 0.20-3)

spam: Sparse Matrix Class

Description

This group of functions evaluates and coerces changes in class structure.

Usage

spam(x, nrow = 1, ncol = 1, eps = .Spam$eps)
as.spam(x, eps = .Spam$eps)
is.spam(x)

Arguments

x

is a matrix (of either dense or sparse form), a list, vector object or a distance object

nrow

number of rows of matrix

ncol

number of columns of matrix

eps

A tolerance parameter: elements of x such that abs(x) < eps set to zero. Defaults to eps = .Spam$eps

Value

• A valid spam object. is.spam returns TRUE if x is a spam object.

Details

The functions spam and as.spam act like matrix and as.matrix to coerce an object to a sparse matrix object of class spam.

If x is a list, it should contain either two or three elements. In case of the former, the list should contain a n by two matrix of indicies (called ind) and the values. In case of the latter, the list should contain three vectors containing the row, column indices (called i and j) and the values. In both cases partial matching is done.

eps should be at least as large as .Machine$double.eps.

References

http://en.wikipedia.org/wiki/Sparse_matrix as a start.

See Also

SPAM general overview of the package. spam.options for details about the safemode flag. read.MM and foreign to create spam matrices from MatrixMarket files and from certain Matrix/SparseM formats.

Examples

# old message, do not loop, when you create a large sparse matrix
set.seed(13)
nz <- 128
ln <- nz^2
smat <- spam(0,ln,ln)
is <- sample(ln,nz)
js <- sample(ln,nz)
system.time(for (i in 1:nz) smat[is[i], js[i]] <- i)
system.time(smat[cbind(is,js)] <- 1:nz)

getClass("spam")



try(as.spam.numeric(NA))