Align Matrix (Vector) on latex

Question

I am trying to align the entries of this vector to the left. Could you help me please? Below is my code and next the result.

P=\left(\begin{matrix}
p^{(1)}(x_1,x_2,\cdots,x_{r_1})  \\
\vdots\\
p^{(m_1)}(x_1,x_2,\cdots,x_{r_1}) \\
p^{(m_1+1)}(x_1,x_2,\cdots,x_{r_1}, x_{r_1+1},x_{r_1+2},\cdots,x_{r_2})  \\
\vdots\\
p^{(m_2)}(x_{r_1+1},x{r_1+_2},\cdots,x_{r_1}, x_1,x_2,\cdots,x_{r_2})    \\
\end{matrix}\right)

...try with \begin{array}{@{}l@{}}...\end{array} instead of \begin{matrix}...\end{matrix}. — Werner, Apr 23 '16 at 13:49
some answers here: How do I left-align entries in a matrix with \begin{matrix}? — barbara beeton, Apr 23 '16 at 15:29

score 7 · Accepted Answer · answered Apr 23 '16 at 13:50

I assume, that you like to have left aligned (now is as is standard for matrices/vector notation. In this case the `array become handy:

\documentclass{article}

    \begin{document}
\[
P=\left(\begin{array}{l}
    p^{(1)}(x_1,x_2,\cdots,x_{r_1})  \\
\vdots\\
    p^{(m_1)}(x_1,x_2,\cdots, x_{r_1}) \\
    p^{(m_1+1)}(x_1,x_2,\cdots,x_{r_1}, x_{r_1+1},x_{r_1+2},\cdots,x_{r_2})  \\
\vdots\\
    p^{(m_2)}(x_{r_1+1},x{r_1+_2},\cdots,x_{r_1}, x_1,x_2,\cdots,x_{r_2})    \\
\end{array}\right)
\]
    \end{document}

score 3 · Answer 2 · answered Apr 23 '16 at 15:06

I propose a slight improvement to @campa's solution, to have a better alignment of the vertical dots:

\documentclass{article}

\usepackage{mathtools}
\usepackage{eqparbox}

\begin{document}
\[
  P=\begin{pmatrix*}[l]
  \eqmakebox[P][l]{$ p^{(1)}(x₁,x₂, ⋯ ,x_{r₁}) $} \\
  \eqmakebox[P]{$ ⋮ $}\\
  \eqmakebox[P]{$ p^{(m₁)}(x₁,x₂, ⋯ ,x_{r₁}) $}\\
  p^{(m₁+1)}(x₁,x₂, ⋯ ,x_{r₁}, x_{r₁+1},x_{r₁+2}, ⋯ ,x_{r₂}) \\
  \eqmakebox[P]{$ ⋮ $}\\
  p^{(m₂)}(x_{r₁+1},x{r₁+₂}, ⋯ ,x_{r₁}, x₁,x₂, ⋯ ,x_{r₂}) \\
  \end{pmatrix*}
\]
\end{document}

Align Matrix (Vector) on latex

2 Answers2