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如何在 Nicematrix 中对选定的列（或行）数量进行过度支撑？

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如何在 Nicematrix 中对选定的列（或行）数量进行过度支撑？

我想突出显示矩阵块，它由其前 3 行和列组成。为了做到这一点，我考虑在前 3 列上放置一个过度支撑，如下图所示：

我想要的矩阵示例

但我还想指定要为哪些列或行扩展矩阵的外部支撑。如何使用 nicematrix 包来实现？下面，它遵循基本的 MWE 来制作我想要的矩阵。

\documentclass{article}



\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{nicematrix}

\usetikzlibrary{matrix}



\begin{document}


\begin{small}           
%   \begin{subequations}
        \begingroup
        \allowdisplaybreaks
        \begin{gather}
            \begin{aligned} 
                \boldsymbol{\mathcal{F}}^{i} & = %
                \begingroup
                    \begin{bNiceMatrix}[%
                    margin,
                    nullify-dots,
                    ]
                        \mathtt{f}_{1\,1} & \Cdots & \mathtt{f}_{1\,\varpi} & \mathtt{f}_{1\,(\varpi+1)} & \Cdots & \mathtt{f}_{1\,\eta} %
                        \\
                        \Vdots & \Ddots & \Vdots & \Vdots & & \Vdots %  
                        \\
                        \mathtt{f}_{\varpi\,1} & \Cdots & \mathtt{f}_{\varpi\,\varpi} & \mathtt{f}_{\varpi\,(\varpi+1)} & \Cdots & \mathtt{f}_{\varpi\,\eta} %
                        \\
                        \noalign{\kern2mm}
                        \mathtt{f}_{(\varpi+1)\,1} & \Cdots & \mathtt{f}_{(\varpi+1)\,\varpi} & \mathtt{f}_{(\varpi+1)\,(\varpi+1)} & \Cdots & \mathtt{f}_{(\varpi+1)\,\eta} %
                        \\
                        \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots %
                        \\
                        \mathtt{f}_{\eta\,1} & \Cdots & \mathtt{f}_{\eta\,\varpi} & \mathtt{f}_{\eta\,(\varpi+1)} & \Cdots & \mathtt{f}_{\eta\,\eta} %
                    \end{bNiceMatrix}%
                \endgroup%  
            \end{aligned}   
        \end{gather}
        \endgroup
%   \end{subequations}
\end{small}


\end{document}

答案1

您可以使用code-after钩子来添加支架。

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{nicematrix}
\usetikzlibrary{decorations.pathreplacing,calligraphy}

\begin{document}

\begin{small}           
%   \begin{subequations}
        \begingroup
        \allowdisplaybreaks
        \begin{gather}
            \begin{aligned} 
                \boldsymbol{\mathcal{F}}^{i} & = %
                \begingroup
                    \begin{bNiceMatrix}[%
                    margin,
                    nullify-dots,
                    code-after = {\begin{tikzpicture}[
                        decoration={calligraphic brace, amplitude=6pt,raise=2pt}]
                    \draw[decorate,thick] (1-1.north west) -- (1-3.north east)
                    node[midway,above=1.5ex]{$\scriptstyle\mathcal{F}_N^i$};
                    \end{tikzpicture}}
                    ]
                        \mathtt{f}_{1\,1} & \Cdots & \mathtt{f}_{1\,\varpi} & \mathtt{f}_{1\,(\varpi+1)} & \Cdots & \mathtt{f}_{1\,\eta} %
                        \\
                        \Vdots & \Ddots & \Vdots & \Vdots & & \Vdots %  
                        \\
                        \mathtt{f}_{\varpi\,1} & \Cdots & \mathtt{f}_{\varpi\,\varpi} & \mathtt{f}_{\varpi\,(\varpi+1)} & \Cdots & \mathtt{f}_{\varpi\,\eta} %
                        \\
                        \noalign{\kern2mm}
                        \mathtt{f}_{(\varpi+1)\,1} & \Cdots & \mathtt{f}_{(\varpi+1)\,\varpi} & \mathtt{f}_{(\varpi+1)\,(\varpi+1)} & \Cdots & \mathtt{f}_{(\varpi+1)\,\eta} %
                        \\
                        \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots %
                        \\
                        \mathtt{f}_{\eta\,1} & \Cdots & \mathtt{f}_{\eta\,\varpi} & \mathtt{f}_{\eta\,(\varpi+1)} & \Cdots & \mathtt{f}_{\eta\,\eta} %
                    \end{bNiceMatrix}%
                \endgroup%  
            \end{aligned}   
        \end{gather}
        \endgroup
%   \end{subequations}
\end{small}

\end{document}

在此处输入图片描述

如果您还想像屏幕截图中那样添加 pmatrix 括号，可以执行以下操作。

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{nicematrix}
\usetikzlibrary{decorations.pathreplacing,calligraphy}
\tikzset{block matrix/.style={path picture={
\draw ([xshift=#1,yshift=\pgflinewidth/2]path picture bounding box.south west)
 -| ([xshift=\pgflinewidth/2,yshift=-\pgflinewidth/2]path picture bounding box.north west)
  -- ++ (#1-\pgflinewidth/2,0)
  ([xshift=-#1,yshift=\pgflinewidth/2]path picture bounding box.south east)
 -| ([xshift=-\pgflinewidth/2,yshift=-\pgflinewidth/2]path picture bounding box.north east)
  -- ++ (-#1+\pgflinewidth/2,0);
}},block matrix/.default=0.8ex}
\begin{document}

\begin{small}           
%   \begin{subequations}
        \begingroup
        \allowdisplaybreaks
        \begin{gather}
            \begin{aligned} 
                \boldsymbol{\mathcal{F}}^{i} & = %
                \begingroup
                    \begin{bNiceMatrix}[%
                    margin,
                    nullify-dots,
                    code-after = {\begin{tikzpicture}[
                        decoration={calligraphic brace, amplitude=6pt,raise=2pt}]
                    \node[inner xsep=1ex,fit=(1-1) (3-3),block matrix,thick](block){};
                    \draw[decorate,thick] (block.north west) -- (block.north east)
                    node[midway,above=1.5ex]{$\scriptstyle\mathcal{F}_N^i$};
                    \end{tikzpicture}}
                    ]
                        \mathtt{f}_{1\,1} & \Cdots & \mathtt{f}_{1\,\varpi} & \mathtt{f}_{1\,(\varpi+1)} & \Cdots & \mathtt{f}_{1\,\eta} %
                        \\
                        \Vdots & \Ddots & \Vdots & \Vdots & & \Vdots %  
                        \\
                        \mathtt{f}_{\varpi\,1} & \Cdots & \mathtt{f}_{\varpi\,\varpi} & \mathtt{f}_{\varpi\,(\varpi+1)} & \Cdots & \mathtt{f}_{\varpi\,\eta} %
                        \\
                        \noalign{\kern2mm}
                        \mathtt{f}_{(\varpi+1)\,1} & \Cdots & \mathtt{f}_{(\varpi+1)\,\varpi} & \mathtt{f}_{(\varpi+1)\,(\varpi+1)} & \Cdots & \mathtt{f}_{(\varpi+1)\,\eta} %
                        \\
                        \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots %
                        \\
                        \mathtt{f}_{\eta\,1} & \Cdots & \mathtt{f}_{\eta\,\varpi} & \mathtt{f}_{\eta\,(\varpi+1)} & \Cdots & \mathtt{f}_{\eta\,\eta} %
                    \end{bNiceMatrix}%
                \endgroup%  
            \end{aligned}   
        \end{gather}
        \endgroup
%   \end{subequations}
\end{small}

\end{document}

在此处输入图片描述

答案2

6.4 版nicematrix(2021/11/23) 提供了新的命令\OverBrace和\UnderBrace可用于\CodeAfter解决这种情况。括号是标准 LaTeX 的括号（即用当前数学字体构造的括号），而不是 Tikz 的括号。

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{nicematrix}

\begin{document}

\begin{small}           
\begin{equation*}
\newcommand{\ff}{\mathtt{f}}
\boldsymbol{\mathcal{F}}^{i} = 
\begin{bNiceMatrix}[margin,nullify-dots]
    \ff_{1\,1} & \Cdots & \ff_{1\,\varpi} & \ff_{1\,(\varpi+1)} & \Cdots & \ff_{1\,\eta} \\
    \Vdots & \Ddots & \Vdots & \Vdots & & \Vdots \\
    \ff_{\varpi\,1} & \Cdots & \ff_{\varpi\,\varpi} & \ff_{\varpi\,(\varpi+1)} & \Cdots & \ff_{\varpi\,\eta} \\
    \noalign{\kern2mm}
    \ff_{(\varpi+1)\,1} & \Cdots & \ff_{(\varpi+1)\,\varpi} & \ff_{(\varpi+1)\,(\varpi+1)} & \Cdots & \ff_{(\varpi+1)\,\eta} \\
    \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots \\
    \ff_{\eta\,1} & \Cdots & \ff_{\eta\,\varpi} & \ff_{\eta\,(\varpi+1)} & \Cdots & \ff_{\eta\,\eta} 
\CodeAfter
  \SubMatrix[{1-1}{3-3}][slim,extra-height=-1mm,xshift=1mm]
  \OverBrace{1-1}{3-3}{\scriptstyle\mathcal{F}_N^i}[shorten,yshift=1mm]
\end{bNiceMatrix}
\end{equation*}
\end{small}

\end{document}

与往常一样nicematrix，您需要进行多次编译。

上述代码的输出

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