# highlighting a matrix part by curly bracket

Hi, I want to highlight $J$, $I_{n_2}$, $I_{n_1}$ and $N$ of the matrix above, by curly brackets or anything suitable. Could anyone help me how to do that?

I just want to people to know that I have found a matrix of the form in which I have a non zero $J$ block and $I$ block, $N$ block . You can give me an example by a small matrix.

• What code are you using to obtain the result to this point? – Steven B. Segletes Mar 17 '17 at 12:39
• Please don't post your code as a comment. You can edit your answer and mark it as code so it gets formatted right. And don't post your entire code. Just the parts necessary to obtain the results you show. – Skillmon Mar 17 '17 at 12:45

A solution with blkarray:

\documentclass[a4paper,12pt]{report}%
\usepackage[utf8]{inputenc}
\usepackage[english]{babel} %
\usepackage{amssymb, amsthm} %
\usepackage{mathtools, nccmath}
\usepackage{blkarray} %
\usepackage{bm} %

\begin{document}

\begin{align*}
\renewcommand\arraystretch{1.33}
&  =   \begin{blockarray}{[c]}
\rule{0pt}{14ex} \begin{blockarray}{*{7}{r}}
\begin{block}{|*{4}{r}|*{3}{r}}
\cline{1-4}
0 & 3 & -2           & 0            & 0 & 0 & 0 \\
0 & 1 & \mfrac{2}{3} & \mfrac{5}{3} & 0 & 0 & 0 \\
0 & 0 & 0            & -1           & 0 & 0 & 0 \\
0 & 0 & \mfrac{2}{3} & \mfrac{5}{3} & 0 & 0 & 0 \\[1ex]
\end{block}
\hline
\begin{block}{*{4}{r}|*{3}{r}|}
0 & 0 & 0            & 0            & 1 & 0 & 0 \\
0 & 0 & 0            & 0            & 0 & 1 & 0 \\
0 & 0 & 0            & 0            & 0 & 0 & 1 \\
\cline{5-7}
\end{block}
\end{blockarray}
\end{blockarray}
-λ \begin{blockarray}{[c]}%
\rule{0pt}{13ex} \begin{blockarray}{*{7}{r}}
\begin{block}{|*{4}{r}|*{3}{r}}
\cline{1-4}
1 & 0 & 0            & 0            & 0 & 0 & 0 \\
0 & 1 & 0            & 0            & 0 & 0 & 0 \\
0 & 0 & 1            & 0            & 0 & 0 & 0 \\
0 & 0 & 0            & 1            & 0 & 0 & 0 \\
\end{block}%
\hline
\begin{block}{*{4}{r}|*{3}{r}|}
0 & 0 & 0            & 0            & 0 & 0 & 0 \\
0 & 0 & 0            & 0            & 0 & 0 & 0 \\
0 & 0 & 0            & 0            & 0 & 0 & 0 \\
\cline{5-7}
\end{block}
\end{blockarray}
\end{blockarray}\\
&  =
\begin{bmatrix}
J & 0\\0 & I_{n₂}
\end{bmatrix}
-λ \begin{bmatrix}
I_{n₁} & 0\\0 & N
\end{bmatrix}
\end{align*}%
\end{document}