1. ## special matrix product

Hi, I'm not native English, what is the name the following product. Let a n-column vector and b m-row vector, than c = a × b resultes a n-by-m-matrix:
c_ij = a_i * b_j.

2. Originally Posted by Skalkaz
Hi, I'm not native English, what is the name the following product. Let a n-column vector and b m-row vector, than c = a × b resultes a n-by-m-matrix:
c_ij = a_i * b_j.
i don't know if there's a name for this but what you've defined is simply this $\displaystyle \bold{c}=(\bold{ba})^T.$

3. What does ba mean?
b and a are vector, and n <>= m.

This product is very usefull sometimes,for example:
the matrix of the tranformation r --> a(br) is
T = a × b
where a, b, r is spatial vector, and br is scalar product

4. $\displaystyle \bold{b}$ is an $\displaystyle m \times 1$ vector and $\displaystyle \bold{a}$ an $\displaystyle 1 \times n.$ so $\displaystyle \bold{b}\bold{a}$ is an $\displaystyle m \times n$ matrix. clearly $\displaystyle (\bold{b}\bold{a})^T$ would be the matrix that you called $\displaystyle \bold{c}.$

5. Oh, you are absolutly right.