http://www.endmemo.com/program/R/crossprod.php
R crossprod Function
crossprod() function returns matrix cross-product.crossprod(x, y = NULL) tcrossprod(x, y = NULL)
x: numeric matrixy: numeric matrix, if y=NULL, y is the same as x...> x <- matrix(1:9,3,3) > x
[,1] [,2] [,3] [1,] 1 4 7 [2,] 2 5 8 [3,] 3 6 9
> crossprod(x)
[,1] [,2] [,3] [1,] 14 32 50 [2,] 32 77 122 [3,] 50 122 194
> tcrossprod(x)
[,1] [,2] [,3] [1,] 66 78 90 [2,] 78 93 108 [3,] 90 108 126
