Látex vectorial de columna
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
y &= \begin{bmatrix}
x_{1} \\
x_{2} \\
\vdots \\
x_{m}
\end{bmatrix}
\end{align}
\end{document}
Naughty Nightingale