How to display a distance matrix in LaTeX

Question

I want to show a distance matrix as

in LaTeX, and I try:

\documentclass{article}
\usepackage{amsmath,amssymb}
\begin{document}
We obtain a distance matrix as follows:
$$
\boldsymbol{D}={d_{ij}}=
\begin{array}{c}
\begin{matrix}  1 & 2 & 3 & 4 & 5 \end{matrix}
\
\begin{matrix} 1 \ 2 \ 3 \ 4 \ 5 \end{matrix}
\begin{bmatrix}
0 & & & & \
9 & 0 & & & \
3 & 7 & 0 & & \
6 & 5 & 9 & 0 & \
11 & 10 & 2 & 8 & 0
\end{bmatrix}
\end{array}
$$
\end{document}

It shows

which displays a mediocre result, and the alignment of the result (which I am not very satisfied with) can still be improved.

If one only use basic \usepackage{amsmath,amssymb} without using other (complex) packages, like \usepackage{kbordermatrix}, how can one improve the alignment in a concise and elegant way? P.S.: Simple native LaTeX commands can be easily applied to Markdown mathematical equations.

Also, try to avoid using manual adjustments like \qquad, \quad, \:, \;, etc., for spacing in LaTeX. This is because if the numbers inside the matrix change (e.g., from 2 to 200), it will further increase the alignment workload.

Answer 1

You can use nicematrix.

\documentclass{article}
\usepackage{amsmath,amssymb,bm,nicematrix}
\begin{document}
We obtain a distance matrix as follows:
[
\bm{D}={d_{ij}}=
\begin{bNiceMatrix}[
  first-row,first-col,
  code-for-first-row=\scriptstyle,
  code-for-first-col=\scriptstyle,
]
  &  1 &  2 & 3 & 4 & 5 \
1 &  0 &    &   &   &   \
2 &  9 &  0 &   &   &   \
3 &  3 &  7 & 0 &   &   \
4 &  6 &  5 & 9 & 0 &   \
5 & 11 & 10 & 2 & 8 & 0
\end{bNiceMatrix}
]
\end{document}

Avoid $$ in LaTeX, see Why is \[ ... \] preferable to $$ ... $$?

Answer 2

You could use inner arrays with fixed column width to ensure on the same alignment. The bottom array can be enclosed around a scaled squared brackets. This is still prone to misalignment as well as column width would need to be adjusted every time you update the content. Check if this approach can pass the conversion.

The code

\documentclass{article}
\usepackage{array}
\usepackage{amsmath}
\usepackage{amssymb}
\setlength\arraycolsep{3pt}
\newlength\collen
\settowidth\collen{$00$}
\newcolumntype{D}{>{\centering\arraybackslash}p{\collen}}
\begin{document}
We obtain a distance matrix as follows:
[
  \boldsymbol{D} = {d_{ij}} =
  \begin{array}{c@{}c}
    & \begin{array}{5{D}}
        1 & 2 & 3 & 4 & 5
      \end{array} \[3pt]
    \begin{array}{r} 1 \ 2 \ 3 \ 4 \ 5 \end{array}
    & \left[
        \begin{array}{5{D}}
          0  &    &   &   &   \
          9  & 0  &   &   &   \
          3  & 7  & 0 &   &   \
          6  & 5  & 9 & 0 &   \
          11 & 10 & 2 & 8 & 0
        \end{array}
      \right]
  \end{array}
]
\end{document}

Answer 3

Using a simple blkarray package more easy.

\documentclass[12pt]{article}
\usepackage{amsmath,amssymb,blkarray}
\begin{document}
\[
  \mathbf{D}=\{d_{ij}\}=
    \begin{blockarray}{ccccccc}
        & {\scriptstyle 1} & {\scriptstyle 2} & {\scriptstyle 3} & {\scriptstyle 4} & {\scriptstyle 5}\\
      \begin{block}{c[ccccc]c}
       {\scriptstyle1} & 0 & & & & & \\
      {\scriptstyle 2}& 9 & 0 & & & & \\
       {\scriptstyle 3}& 3 & 7 & 0 & & & \\
      {\scriptstyle 4}& 6 & 5 & 9 & 0 & & \\
      {\scriptstyle 5}&11 & 10 & 2 & 8 & 0 &\\
      \end{block}
      \end{blockarray}
\]
\end{document}