Centering a matrix in a figure?

Question

I have a matrix that I would like to be centered in the middle of the page, however it is showing up left-aligned.

\begin{figure}[ht]$
\centering
    \begin{bmatrix}
        0       & C_l       & 0         & 0         & \dots     & \dots     & \dots     & 0         \\
        0       & 0         & C_l       & 0         & \dots     & \dots     & \dots     & \vdots    \\
        0       & C_r       & 0         & C_l       & \dots     & \dots     & \dots     & \vdots    \\
        0       & 0         & C_r       & 0         & \ddots    & \dots     & \dots     & \vdots    \\
        \vdots  & \hdots    & \hdots    & \ddots    & \ddots    & \ddots    & \hdots    & \vdots    \\
        \vdots  & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & C_l       & 0         \\
        \vdots  & \hdots    & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & 0         \\
        0       & \hdots    & \hdots    & \hdots    & \hdots    & \hdots    & C_r       & 0         \\
    \end{bmatrix}$
\caption{$n \times n$ transition matrix for a classical random walk.}
\end{figure}

How can I center this matrix?

Answer 1

Just move the \centering out of the math material enclosed in $...$.

\documentclass[a4paper]{article}
\usepackage{amsmath}
\begin{document}
\begin{figure}[ht]
\centering
    $\begin{bmatrix}
        0       & C_l       & 0         & 0         & \dots     & \dots     & \dots     & 0         \\
        0       & 0         & C_l       & 0         & \dots     & \dots     & \dots     & \vdots    \\
        0       & C_r       & 0         & C_l       & \dots     & \dots     & \dots     & \vdots    \\
        0       & 0         & C_r       & 0         & \ddots    & \dots     & \dots     & \vdots    \\
        \vdots  & \hdots    & \hdots    & \ddots    & \ddots    & \ddots    & \hdots    & \vdots    \\
        \vdots  & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & C_l       & 0         \\
        \vdots  & \hdots    & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & 0         \\
        0       & \hdots    & \hdots    & \hdots    & \hdots    & \hdots    & C_r       & 0         \\
    \end{bmatrix}$
\caption{$n \times n$ transition matrix for a classical random walk.}
\end{figure}
\end{document}

Answer 2

If you want a figure (floating), replace $\begin{bmatrix} ... $ with \begin{equation*}\begin{bmatrix} ... \end{equation*}:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{figure}[ht]
\centering
\begin{equation*}
    \begin{bmatrix}
        0       & C_l       & 0         & 0         & \dots     & \dots     & \dots     & 0         \\
        0       & 0         & C_l       & 0         & \dots     & \dots     & \dots     & \vdots    \\
        0       & C_r       & 0         & C_l       & \dots     & \dots     & \dots     & \vdots    \\
        0       & 0         & C_r       & 0         & \ddots    & \dots     & \dots     & \vdots    \\
        \vdots  & \hdots    & \hdots    & \ddots    & \ddots    & \ddots    & \hdots    & \vdots    \\
        \vdots  & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & C_l       & 0         \\
        \vdots  & \hdots    & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & 0         \\
        0       & \hdots    & \hdots    & \hdots    & \hdots    & \hdots    & C_r       & 0         \\
    \end{bmatrix}
\end{equation*}

\caption{$n \times n$ transition matrix for a classical random walk.}
\end{figure}


\end{document}

Answer 3

My solution is suited for 'fixed' positioning of content with a caption, i.e. the content should not float around.

\documentclass[10pt]{book}

\usepackage{caption}
\usepackage{amsmath}

\begin{document}

\chapter{My very sophisticated matrix}
\begingroup
\centering%
\(%
    \begin{bmatrix}%
        0       & C_l       & 0         & 0         & \dots     & \dots     & \dots     & 0         \\
        0       & 0         & C_l       & 0         & \dots     & \dots     & \dots     & \vdots    \\
        0       & C_r       & 0         & C_l       & \dots     & \dots     & \dots     & \vdots    \\
        0       & 0         & C_r       & 0         & \ddots    & \dots     & \dots     & \vdots    \\
        \vdots  & \hdots    & \hdots    & \ddots    & \ddots    & \ddots    & \hdots    & \vdots    \\
        \vdots  & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & C_l       & 0         \\
        \vdots  & \hdots    & \hdots    & \hdots    & \hdots    & \ddots    & \ddots    & 0         \\
        0       & \hdots    & \hdots    & \hdots    & \hdots    & \hdots    & C_r       & 0         \\
    \end{bmatrix}%
\)%
\captionof{figure}{$n \times n$ transition matrix for a classical random walk.}%
\endgroup%
\end{document}