How can I type this form of a matrix in LaTeX?

How can I type this form of a matrix in LaTeX?

Use the kbordermatrix package. (I think for licence reasons it cannot be included in the TeX distributions.)

\documentclass{article}
\usepackage{rotating}
\usepackage{kbordermatrix}
\begin{document}
$C = \raisebox{-2\baselineskip}{% \begin{tabular}[b]{c@{\hspace*{0.5em}}c} & To node \\ \begin{sideways} From node \end{sideways} & \raisebox{0.5\height}% {$$\kbordermatrix { & 1 & 2 & 3 & 4 & 5 \\ 1 & 1 & x_1 & x_5 & 0 & 0 \\ 2 & x_1 & 1 & x_2 & x_3 & x_4 \\ 3 & x_5 & x_2 & 1 & x_6 & 0 \\ 4 & 0 & x_3 & x_6 & 1 & x_7 \\ 5 & 0 & x_4 & 0 & x_7 & 1 }$$% } \end{tabular}}$
\end{document}

• kbordermatrix is included in MiKTeX distribution... – Arzigoglu Dec 22 '16 at 18:46

Something similar can be done with TikZ. The baseline correction of the matrix is achieved by means of egreg’s formula.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
$C = \begin{tikzpicture}[baseline={([yshift=-\dimexpr\fontdimen22\textfont2\relax]M.center)}] \matrix [ matrix of math nodes, left delimiter={[}, right delimiter={]}, inner sep=1pt, column sep=1ex, row sep=1ex, execute at begin cell=\mathstrut, ] (M) { 1 & x_1 & x_5 & 0 & 0 \\ x_1 & 1 & x_2 & x_3 & x_4 \\ x_5 & x_2 & 1 & x_6 & 0 \\ 0 & x_3 & x_6 & 1 & x_7 \\ 0 & x_4 & 0 & x_7 & 1 \\ }; \foreach \c in {1,...,5} \node[above=1em] at (M-1-\c) {\scriptstyle\c}; \foreach \r in {1,...,5} \node[left=1.5em] at (M-\r-1) {\scriptstyle\r}; \node[above=2em] at (M-1-3) {To node}; \node[rotate=90,above=2.5em] at (M-3-1) {From node}; \end{tikzpicture}$
\end{document}