[Tex/LaTex] Block matrices, separator with space

arraysmatrices

I want to write block matrices like the one shown below block matrix image

I tried underlining, fraction, and using __ as an entry by making three rows but they did not look nice.I want the horizontal lines inside the matrix to be gapped in between as shown. How can I do this?

Best Answer

This is one way:

\documentclass[a4paper,journal]{IEEEtran}
\usepackage{amsmath}

\begin{document}
\[
\begin{bmatrix}
  \frac{I}{\mathrm{O}}\frac{\mathrm{O}}{\mathrm{O}}
\end{bmatrix}
\begin{bmatrix}
  \frac{x}{u}
\end{bmatrix} =
\begin{bmatrix}
  \frac{A}{C}\frac{B}{D}
\end{bmatrix}
\begin{bmatrix}
  \frac{x}{u}
\end{bmatrix} +
\begin{bmatrix}
  \frac{\mathrm{O}}{-y}
\end{bmatrix}
\]
%
\[
\left[
  \frac{I}{\mathrm{O}}\frac{\mathrm{O}}{\mathrm{O}}
\right]
\left[
  \frac{x}{u}
\right] =
\left[
  \frac{A}{C}\frac{B}{D}
\right]
\left[
  \frac{x}{u}
\right] +
\left[
  \frac{\mathrm{O}}{-y}
\right]
\]
\end{document}

enter image description here

Instead of dynamically varying brackets (\left[ and \right]), you may use fixed size brackets like \Bigg[ and \Bigg] provided by amsmath.

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