Extend vertically \langle and \rangle - paranthesis an environment {NiceMatrix} with Tikz-PGF

Question

I'd like to extend vertically the \langle and \rangle -paranthesis in this code:

\documentclass{article}
\usepackage[customcolors,shade]{hf-tikz}
\usepackage{nicematrix}
\usepackage{diagbox}
\usepackage{tikz-cd}
[\begin{NiceMatrix}[columns-width=8.5mm]
\diagbox{\small A_i} {\small A^j} 
\Block[hvlines]{1-4}{}
\Block[hvlines]{4-1}{}
& A^1 & A^2 & A^3 \
A_1 & 1 & 2 & 3 \
A_2 & 4 & 5 & 6 \
A_3 & 7 & 8 & 9 
\CodeAfter
\SubMatrix\langle{2-2}{4-4}\rangle[xshift=-0.85mm]
\begin{tikzpicture} [dashed,shorten > = 2mm, shorten < = 2mm]
  \draw (3-|2) -- (3-|5) ;
  \draw (4-|2) -- (4-|5) ;
  \draw (2-|3) -- (5-|3) ;
  \draw (2-|4) -- (5-|4) ;
%[line,shorten > = 2mm, shorten < = 2mm]
  \end{tikzpicture}
\begin{tikzpicture}
\draw (2-|5) -- (5-|5) ;
\draw (5-|2) -- (5-|5) ;
\end{tikzpicture}
\end{NiceMatrix}]
\end{document}

Thank you so much

You mean "extend vertically"? – F. Pantigny Jul 01 '21 at 11:00 — F. Pantigny, Jul 01 '21 at 11:00
Yes, I have just edited my question – Puck Jul 01 '21 at 11:02 — Puck, Jul 01 '21 at 11:02

score 1 · Answer 1 · answered Jul 01 '21 at 11:12

The command \SubMatrix available in the \CodeAfter of the environments of nicematrix has a key extra-height to increase the vertical size of the delimiters.

\documentclass{article}
\usepackage{nicematrix}
\usepackage{tikz}
\begin{document}
[\begin{NiceMatrix}[columns-width=8.5mm,hvlines]
\diagbox{\scriptstyle A_i} {\scriptstyle A^j} 
& A^1 & A^2 & A^3 \
A_1 & \Block{3-3}{}
      1 & 2 & 3 \
A_2 & 4 & 5 & 6 \
A_3 & 7 & 8 & 9 
\CodeAfter
\SubMatrix[{2-2}{4-4}][xshift=-0.85mm,extra-height=1mm]
\begin{tikzpicture} [dashed,shorten > = 2mm, shorten < = 2mm]
    \draw (3-|2) -- (3-|5) ;
    \draw (4-|2) -- (4-|5) ;
    \draw (2-|3) -- (5-|3) ;
    \draw (2-|4) -- (5-|4) ;
\end{tikzpicture}
\end{NiceMatrix}]
\end{document}

However, the delimiters \langle and \rangle have a maximal size (see that question). In you example, the default size is yet the maximal size and that why extra-height won't have any effect.

You could try to change the mathematical font as explained in the question linked above...

I've just seen this site link but I have trouble with applicate it — Puck, Jul 01 '21 at 11:23
Furthermore, The xshift=-0.85mm, yshift=-0.85mm -commands are not very clear to me. Could You explain, please? — Puck, Jul 01 '21 at 13:16
Does exist a way to write \SubMatrix without parenthesis? Thx — Puck, Jul 01 '21 at 13:40

score 1 · Accepted Answer · answered Jul 01 '21 at 15:01

Here is a solution by drawing the angular brackets with Tikz.

\documentclass{article}
\usepackage{nicematrix}
\usepackage{tikz}
\begin{document}
[
\begin{NiceMatrix}[columns-width=8.5mm,cell-space-limits=2pt,hvlines]
\diagbox{\scriptstyle A_i} {\scriptstyle A^j} 
& A^1 & A^2 & A^3 \
A_1 & \Block{3-3}{}
      1 & 2 & 3 \
A_2 & 4 & 5 & 6 \
A_3 & 7 & 8 & 9 
\CodeAfter
    \begin{tikzpicture} 
    \begin{scope} [dashed]
      \draw ([xshift=3mm]3-|2) -- ([xshift=-3mm]3-|5) ;
      \draw ([xshift=3mm]4-|2) -- ([xshift=-3mm]4-|5) ;
      \draw (2-|3) -- (5-|3) ;
      \draw (2-|4) -- (5-|4) ;
    \end{scope}
    \begin{scope} [line width=1pt] 
      \draw ([xshift=-1mm]2-|2.5) -- ([xshift=1mm]3.5-|2) -- ([xshift=-1mm]5-|2.5) ;
      \draw ([xshift=1mm]2-|4.5) -- ([xshift=-1mm]3.5-|5) -- ([xshift=1mm]5-|4.5) ;
    \end{scope}
    \end{tikzpicture}
\end{NiceMatrix}
]
\end{document}

Comments

The command \Block{3-3}{} creates a empty block. With that block, the key hvlines will draw all the rules excepted in the blocks (in that block, in fact, here).
The command \diagbox is a built-in command of nicematrix. So, there is no need to load the package diagbox.
I have adjusted the positions of the points of the angular brackets by using [xshift=...] in the Tikz coordinates (this is a Tikz feature).
The environment {scope} is provided by Tikz. It's a way to limit the scope of the options in a Tikz picture.
As usual with nicematrix, you need several compilations.

Extend vertically \langle and \rangle - paranthesis an environment {NiceMatrix} with Tikz-PGF

2 Answers2