Notation for a matrix with same vector in columns

Question

Is there a notation for a matrix which columns are the same vector?

$$ x = \left[\begin{array}{ccc}x_1 & x_2 & x_3\end{array}\right]^{T} \\ y = \left[\begin{array}{ccc}x & x & x\end{array}\right] $$

Is there a proper notation for $y$?

Answer 1

The notation you have for $y$ is fine. It's common block matrix notation.

Answer 2

Sometimes I've seen it wrote like this $$\left(\begin{matrix} |&|&|\\x&x&x\\|&|&|\end{matrix}\right)$$ The form you suggested doesn't seems right to me, but I could be wrong!