# crossprod: Matrix Crossproduct In slam: Sparse Lightweight Arrays and Matrices

## Description

Compute the matrix cross-product of a sparse and a dense or sparse matrix.

## Usage

 ```1 2 3 4``` ```tcrossprod_simple_triplet_matrix(x, y = NULL) ## crossprod_simple_triplet_matrix(x, y = NULL) matprod_simple_triplet_matrix(x, y) ```

## Arguments

 `x, y` a matrix in `simple_triplet_matrix`-form and/or a dense matrix, where one must be of the form indicated by the suffix.

## Details

Function `tcrossprod_simple_triplet_matrix` implements fast computation of `x %*% t(x)` and `x %*% t(y)` (`tcrossprod`). The remaining functions are (optimized) wrappers.

## Value

A double matrix, with appropriate `dimnames` taken from `x` and `y`.

## Note

The computation is delegated to `tcrossprod` if `y` (or `x` if `y == NULL`) contains any of the special values `NA`, `NaN`, or `Inf`.

## Author(s)

Christian Buchta

`crossprod` for dense-on-dense computations.

## Examples

 ```1 2 3 4 5 6 7 8 9``` ```## x <- matrix(c(1, 0, 0, 2, 1, 0), nrow = 3) x s <- as.simple_triplet_matrix(x) tcrossprod_simple_triplet_matrix(s, x) ## tcrossprod_simple_triplet_matrix(s) ## tcrossprod_simple_triplet_matrix(s[1L, ], s[2:3, ]) ```

slam documentation built on Dec. 23, 2017, 5:15 p.m.