Matrices in Linear Algebra
If I need to do the dot product of a vector and a matrix, is it commutative?
ex. I have a 3 by 3 matrix that has a dot next to a 1 row vector with 3 columns. If it's commutative, I can get an answer but if not I can't.
September 24, 2013
6 Comments • Newest first
[quote=Al3xL3g3nd]All I know:
Dot products are commutative if both vectors have the same size.
Dot products are not commutative if they are both matrices.
So what about the dot product between a matrix and a vector?
Also, I messed up the first part of the question so I don't need the answer anymore but I would like to know for future reference.[/quote]
Your 1 row "vector" is essentially a 1x3 matrix. So therefore its not commutative.
The only commutative thing I know of matrices is when you multiply it by a SCALAR and the Identity matrix.
All I know:
Dot products are commutative if both vectors have the same size.
Dot products are not commutative if they are both matrices.
So what about the dot product between a matrix and a vector?
Also, I messed up the first part of the question so I don't need the answer anymore but I would like to know for future reference.
Matrices are not commutative.
dot products are commutative, it is the definition of distance
no, matrices are not commutative. even if you were to take the transpose of the vector, and multiply on the other side (so multiplication is defined), and take the transpose of the result, the answer will be different, in general.
yes i do too