Wikipedia seems to disagree. I also knew it the same way as wikipedia states, before.
http://en.wikipedia.org/wiki/Cross_product On Sun, Dec 25, 2011 at 3:39 PM, Raphael Cendrillon <[email protected]> wrote: > I think the cross product is typically used to refer to the outer product, > while the dot product refers to the inner product. > > On Dec 25, 2011, at 2:51 PM, Ted Dunning <[email protected]> wrote: > >> This is misleading even if not strictly incorrect. In matrix terminology, >> outer product is definitely more commonly used. >> >> On Sun, Dec 25, 2011 at 1:37 PM, Dmitriy Lyubimov <[email protected]> wrote: >> >>> Hello, >>> >>> just stumbled on this in vector while looking for outer product operation >>> -- >>> >>> @Override >>> public Matrix cross(Vector other) { >>> Matrix result = matrixLike(size, other.size()); >>> for (int row = 0; row < size; row++) { >>> result.assignRow(row, other.times(getQuick(row))); >>> } >>> return result; >>> } >>> >>> >>> It seems this guy computes an outer product, but not cross product ( >>> crossprod for vectors =ab sin(theta)n). Seems like a misleading >>> naming. >>> >>> It is probably motivated by R, where tcrossproduct (which is a product >>> of matrices, not vectors) is defined as XY' and crossprod which is >>> defined X'Y and so in case of cbind(vector) it would constitute either >>> dot product or outer product respectively. But i am not sure where R >>> is deriving this; and even then it is definitely misleading as R would >>> apply this to the world of matrices, not vectors. In vectors cross >>> product means something else and i think this may create a confusion >>> (it certainly did in my case).. >>> >>> thanks. >>> -Dmitriy >>>
