Given matrices x and y as arguments, return a matrix cross-product. This is formally equivalent to (but usually slightly faster than) the call t(x) %*% y (crossprod) or x %*% t(y) (tcrossprod).
crossprod(x, y = NULL)<p></p><p>tcrossprod(x, y = NULL)</p>| Parameter | Description |
|---|---|
x, y |
numeric or complex matrices (or vectors): y = NULL is taken to be the same matrix as x. Vectors are promoted to single-column or single-row matrices, depending on the context. |
# NOT RUN {
(z <- crossprod(1:4)) # = sum(1 + 2^2 + 3^2 + 4^2)
drop(z) # scalar
x <- 1:4; names(x) <- letters[1:4]; x
tcrossprod(as.matrix(x)) # is
identical(tcrossprod(as.matrix(x)),
crossprod(t(x)))
tcrossprod(x) # no dimnames
m <- matrix(1:6, 2,3) ; v <- 1:3; v2 <- 2:1
stopifnot(identical(tcrossprod(v, m), v %*% t(m)),
identical(tcrossprod(v, m), crossprod(v, t(m))),
identical(crossprod(m, v2), t(m) %*% v2))
# }