如何使用 Nicematrix 和 TikZ 在我的矩阵下绘制一个花括号来描述我的列？

Question

我想在我的矩阵下画两个大括号来表示向量 a 与向量 x 不同并解释原因。尽管如此，我目前的尝试只是在我的矩阵中间画了一个大括号......有人有想法吗？ 我尝试在这里添加一个sn-p，我的代码也在这里：https://www.overleaf.com/read/nnkpkdrwphmd

非常感谢您的帮助！

\documentclass{article}
\usepackage{nicematrix}
\usepackage{tikz}
\usepackage[utf8]{inputenc}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usetikzlibrary{patterns}
\usetikzlibrary{matrix,decorations.pathreplacing}
\usetikzlibrary{decorations.pathreplacing,calligraphy}

\title{Fairness}
\author{someone}
\date{May 2021}

\begin{document}

\maketitle

\section{Introduction}

\NiceMatrixOptions{code-for-first-row = \color{red},
    code-for-first-col = \color{blue},
    code-for-last-row = \color{green},
    code-for-last-col = \color{magenta}}

$\begin{pNiceMatrix}%
[margin,
first-row,
first-col,
%code-for-first-row = \mathbf{\alph{jCol}} ,
%code-for-first-col = \mathbf{\arabic{iRow}} ,
nullify-dots,
xdots/line-style=loosely dotted,
code-after = {\begin{tikzpicture}[decoration={calligraphic brace, mirror, amplitude=6pt,raise=2pt}]
                \draw[decorate,thick] (0-1.south south) -- (1-3.south east);
                node[midway,under=1.5ex]{$\scriptstyle\mathcal{A}_N^i$};
                \end{tikzpicture}}
]
&        1             & 2           & \Cdots    & k         & k+1          & k+2          & \Cdots  & m          \\
1        & a_{(1,1)}   & a_{(1,2)}   & \Cdots    & a_{(1,k)} & x_{(1,k+1)}  & x_{(1,k+2)}  & \Cdots  & x_{(1,m)}  \\
2        & a_{(2,1)}   & a_{(2,2)}   & \Cdots    & a_{(2,k)} & x_{(2,k+1)}  & x_{(2,k+2)}  & \Cdots  & x_{(2,m)}  \\
3        & a_{(3,1)}   & a_{(3,2)}   & \Cdots    & a_{(3,k)} & x_{(3,k+1)}  & x_{(3,k+2)}  & \Cdots  & x_{(3,m)}  \\
\Vdots   & \Vdots      & \Ddots      & \Cdots    & \Vdots    & \Vdots       & \Ddots       & \Cdots  & \Vdots     \\
&        &             & \Cdots      &           &           &              & \Cdots       &         &            \\
n        & a_{(n,1)}   & a_{(n,2)}   & \Cdots    & a_{(n,k)} & x_{(n,k+1)}  & x_{(n,k+2)}  & \Cdots  & x_{(n,m)}
%\CodeAfter \SubMatrix{\{}{1-1}{3-1}{.}[left-xshift=0.5em]
\end{pNiceMatrix}$

\end{document}

Answer 1

• 你不能在没有定义的情况下使用像under 这样的键

• south south 不是有效的锚点

• 只能使用非空单元格的坐标

---

\documentclass{article}
\usepackage{nicematrix}
\usepackage{tikz}
\usepackage[utf8]{inputenc}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usetikzlibrary{patterns}
\usetikzlibrary{matrix,decorations.pathreplacing}
\usetikzlibrary{decorations.pathreplacing,calligraphy}

\title{Fairness}
\author{someone}
\date{May 2021}

\begin{document}

\maketitle

\section{Introduction}

\NiceMatrixOptions{code-for-first-row = \color{red},
    code-for-first-col = \color{blue},
    code-for-last-row = \color{green},
    code-for-last-col = \color{magenta}}

$\begin{pNiceMatrix}%
[margin,
name=mymatrix,
first-row,
first-col,
%code-for-first-row = \mathbf{\alph{jCol}} ,
%code-for-first-col = \mathbf{\arabic{iRow}} ,
nullify-dots,
xdots/line-style=loosely dotted,
code-after = {\begin{tikzpicture}[decoration={calligraphic brace, mirror, amplitude=6pt,raise=2pt}]
                \draw[decorate,thick] (mymatrix-6-1.south west) -- (mymatrix-6-4.south east) node[midway,yshift=-2em]{a};
                \draw[decorate,thick] (mymatrix-6-5.south west) -- (mymatrix-6-8.south east) node[midway,yshift=-2em]{x};
                \end{tikzpicture}}
]
&        1             & 2           & \Cdots    & k         & k+1          & k+2          & \Cdots  & m          \\
1        & a_{(1,1)}   & a_{(1,2)}   & \Cdots    & a_{(1,k)} & x_{(1,k+1)}  & x_{(1,k+2)}  & \Cdots  & x_{(1,m)}  \\
2        & a_{(2,1)}   & a_{(2,2)}   & \Cdots    & a_{(2,k)} & x_{(2,k+1)}  & x_{(2,k+2)}  & \Cdots  & x_{(2,m)}  \\
3        & a_{(3,1)}   & a_{(3,2)}   & \Cdots    & a_{(3,k)} & x_{(3,k+1)}  & x_{(3,k+2)}  & \Cdots  & x_{(3,m)}  \\
\Vdots   & \Vdots      & \Ddots      & \Cdots    & \Vdots    & \Vdots       & \Ddots       & \Cdots  & \Vdots     \\
&        &             & \Cdots      &           &           &              & \Cdots       &         &            \\
n        & a_{(n,1)}   & a_{(n,2)}   & \Cdots    & a_{(n,k)} & x_{(n,k+1)}  & x_{(n,k+2)}  & \Cdots  & x_{(n,m)}
%\CodeAfter \SubMatrix{\{}{1-1}{3-1}{.}[left-xshift=0.5em]
\end{pNiceMatrix}$

\end{document}

Answer 2

nicematrix (2021-11-23) 6.4 版提供了\CodeAfter 中可用的命令\UnderBrace 和\OverBrace 来绘制水平大括号。大括号是 LaTeX 数学模式的标准大括号（而不是 Tikz 的大括号）。

\documentclass{article}
\usepackage{nicematrix,tikz}

\begin{document}

$\begin{pNiceMatrix}%
  [ 
    code-for-first-row = \color{red},
    code-for-first-col = \color{blue},
    xdots/line-style=loosely dotted,
    parallelize-diags = false,
    first-row,
    first-col,
    nullify-dots,
  ]
         & 1         & 2          & \Cdots & k         & k+1         & k+2         & \Cdots & m     \\
1        & a_{(1,1)} & a_{(1,2)}  & \Cdots & a_{(1,k)} & x_{(1,k+1)} & x_{(1,k+2)} & \Cdots & x_{(1,m)}  \\
2        & a_{(2,1)} & a_{(2,2)}  & \Cdots & a_{(2,k)} & x_{(2,k+1)} & x_{(2,k+2)} & \Cdots & x_{(2,m)}  \\
3        & a_{(3,1)} & a_{(3,2)}  & \Cdots & a_{(3,k)} & x_{(3,k+1)} & x_{(3,k+2)} & \Cdots & x_{(3,m)}  \\
\Vdots   & \Vdots    & \Ddots     &        & \Vdots    & \Vdots      & \Ddots      &        & \Vdots     \\
         &           &            &        &           &             &             &        &            \\
n        & a_{(n,1)} & a_{(n,2)}  & \Cdots & a_{(n,k)} & x_{(n,k+1)} & x_{(n,k+2)} & \Cdots & x_{(n,m)}  
\CodeAfter
  \UnderBrace[shorten,yshift=1.5mm]{last-1}{last-4}{\mathrm{a}}
  \UnderBrace[shorten,yshift=1.5mm]{last-5}{last-last}{\mathrm{x}}
\end{pNiceMatrix}$

\end{document}

与nicematrix 一样，您需要进行多次编译。