Computes the external product $$ \left(x_2 y_3 - x_3 y_2,\; x_3 y_1 - x_1 y_3,\; x_1 y_2 - x_2 y_1 \right) $$ of the 3D vectors in x and y.
extprod3d(x, y, drop = TRUE)If n is greater than 1 or drop is
FALSE, n-by-3 matrix; if n is 1 and
drop is TRUE, a vector of length 3.
n-by-3 matrix. Each row is one x-vector
n-by-3 matrix. Each row is one y-vector
logical. If TRUE and if the inputs are one row
matrices or vectors, then delete the dimensions of the array
returned.
Raoul Grasman