Writing a matrix over two lines

I want to write a big matrix and I want to write it in two lines like the picture but I cannot find the way!

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Oh no.... well ok, I'm calm.10..9..8..7.. factorize tilde d1 d2 d3 d4 with a diagonal matrix from the right for a start..3..2..1 – percusse Feb 25 '14 at 20:45

\documentclass{article}
\usepackage{mathtools}
\def\mtrm#1{\rule{#1}{1.5ex}}

\begin{document}

\begin{multline}
\bar{L}_2 = \left(
\begin{matrix}
\mtrm{15ex} & \mtrm{15ex}\\
\mtrm{7ex}  & \mtrm{7ex} \\
\mtrm{4ex}  & \mtrm{4ex} \\
\mtrm{18ex} & \mtrm{18ex}\\
\end{matrix}\right.
\\
\left.
\begin{matrix}
\mtrm{16ex} & \mtrm{6ex} \\
0           & 0          \\
\mtrm{4ex}  & \mtrm{14ex}\\
\mtrm{19ex} & \mtrm{19ex}
\end{matrix}\right)
\end{multline}

\end{document}


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\documentclass{standalone}

\begin{document}
\begin{tabular}{ccc}
$L=$ & $\left( \begin{tabular}{c}A\\B\\C\\D\\\end{tabular} \right.$ & $\begin{tabular}{c}E\\F\\G\\H\\\end{tabular}$ \\
& $\begin{tabular}{c}I\\J\\K\\L\\\end{tabular}$ & $\left. \begin{tabular}{c}M\\N\\O\\P\\\end{tabular} \right)$\\
\end{tabular}
\end{document}


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Here is a way, with a stacked TABstack. Things to note: the \kern will shift the top and bottom horizontally relative to each other; the [12pt] optional argument of \stackanchor is the vertical spacing between top and bottom halves; the 2ex \setstacktabbedgap is the horizontal gap between matrix columns; if you wanted the equation number in a different vertical location, let me know, so that I can address that.

I will leave you to replace the rules with your math terms. They do NOT need to be enclosed in \$ delimiters.

\documentclass{article}
\usepackage{tabstackengine}
\stackMath
\def\mtrm#1{\protect\rule{#1}{1.5ex}}
\begin{document}
\setstacktabbedgap{2ex} \def\stackalignment{r} \stackanchor[12pt]{% \bar{L}_2 = \left( \tabbedCenterstack[c]{% \mtrm{10ex} & \mtrm{10ex} \\ \mtrm{7ex} & \mtrm{7ex} \\ \mtrm{4ex} & \mtrm{4ex} \\ \mtrm{8ex} & \mtrm{8ex} }% \right.\kern2ex }{ \left. \tabbedCenterstack[c]{% \mtrm{6ex} & \mtrm{6ex} \\ 0 & 0 \\ \mtrm{4ex} & \mtrm{4ex} \\ \mtrm{9ex} & \mtrm{9ex} }% \right)% }
\end{document}


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It doesn't work! LaTeX Error: File tabstackengine.sty' not found. Should I download it separately? – Farzane Feb 25 '14 at 21:26
@Farzane It is a recent package. It can be found at ctan.org/pkg/tabstackengine. Placing the .sty file in your current directory will work (until you figure out where to install it permanently). The .pdf file gives documentation, though I would recommend also reading the docs for stackengine` as well, since the latter builds on the former. – Steven B. Segletes Feb 26 '14 at 2:07