slam (version 0.1-54)

apply: Apply Functions Over Sparse Matrix Margins

Description

Apply functions to (the cross-pairs of) the rows or columns of a sparse matrix.

Usage

rowapply_simple_triplet_matrix(x, FUN, ...)
colapply_simple_triplet_matrix(x, FUN, ...)
crossapply_simple_triplet_matrix(x, y = NULL, FUN, ...) 
tcrossapply_simple_triplet_matrix(x, y = NULL, FUN, ...)

Value

A vector (matrix) of length (dimensionality) of the margin(s) used. The type depends on the result of FUN.

Note that the result of colapply_simple_triplet_matrix is never simplified to matrix.

Arguments

x, y

a matrix in simple_triplet_matrix-form or, one of x and y, of class matrix.

FUN

the name of the function to be applied.

...

optional arguments to FUN.

Author

Christian Buchta

Details

colapply_simple_triplet_matrix temporarily expands each column of x to dense vector representation and applies the function specified in FUN.

crossapply_simple_triplet_matrix temporarily expands each cross-pair of columns of x (and y) to dense vector representation and applies the function specified in FUN.

Note that if y = NULL then only the entries in the lower triangle and the diagonal are computed, assuming that FUN is symmetric.

See Also

apply for dense-on-dense computations.

Examples

## 
x <- matrix(c(1, 0, 0, 2, 1, 0), nrow = 3, 
    dimnames = list(1:3, LETTERS[1:2]))
x
s <- as.simple_triplet_matrix(x)
colapply_simple_triplet_matrix(s, FUN = var)
##
simplify2array(colapply_simple_triplet_matrix(s, identity))
##
crossapply_simple_triplet_matrix(s, FUN = var)