表格格式：仅从特定单元格中删除水平和垂直边框

Question

下面的 MWE 创建了一个 3 x 3 的表格。表格上方的文本描述了我希望没有边框的特定单元格。

我相信解决方案在于正确使用\cline命令并结合\multicolumn{1}{c|}。

但我无法找出正确的语法来实现期望的结果。

非常感谢您的帮助！

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[table]{xcolor}
\setlength{\parskip}{\baselineskip}
\title{FACTORbox}
\author{Algebra Teacher Who Struggles with LaTeX Tables}
\date{January 2021}

\begin{document}

\maketitle
In the table below, I only want \textbf{borderlines around the values in black,
} not the red values above and to the left of the black colored values.

Also, I can't figure out a way to \textbf{remove the gray shading from upper left corner cell.}


\def\arraystretch{2}
\begin{tabular}{ |c | c | c | }
 %  \hline
   \cellcolor{gray}& \textcolor{red}{$x$} & \textcolor{red}{$+6$} \\
   \hline
  \textcolor{red}{$x$} & $x^2$ & $6x$ \\
  \hline 
  \textcolor{red}{$+2$} & $2x$ & $12$ \\
  \hline
\end{tabular}


\end{document}

Answer 1

像这样？

您有很多种可能性，其中之一就是使用\multicolumn没有边框的命令：

\documentclass{article}
\usepackage[table]{xcolor}
\newcommand\mcc[1]{\multicolumn{1}{c}{#1}} % <--- 

\setlength{\parskip}{\baselineskip}
\title{FACTORbox}
\author{Algebra Teacher Who Struggles with LaTeX Tables}
\date{January 2021}

\begin{document}

\maketitle
In the table below, I only want \textbf{borderlines around the values in black,
} not the red values above and to the left of the black colored values.

Also, I can't figure out a way to \textbf{remove the gray shading from upper left corner cell.}


\renewcommand\arraystretch{2}
\begin{tabular}{ c | c | c | }
 %  \hline
 \mcc{} & \mcc{\textcolor{red}{$x$}} & \mcc{\textcolor{red}{$+6$}} \\
    \cline{2-3}
 \textcolor{red}{$x$} & $x^2$ & $6x$ \\
    \cline{2-3}
 \textcolor{red}{$+2$} & $2x$ & $12$ \\
    \cline{2-3}
\end{tabular}


\end{document}

编辑：

另一种可能性是使用˙blkarray包：

\documentclass{article}
\usepackage[table]{xcolor}
\usepackage{blkarray}

\begin{document}
$\renewcommand\arraystretch{2}
\begin{blockarray}{r cc}
    & \textcolor{red}{x} & \textcolor{red}{+6}   \\
    \cline{2-3}
    \begin{block}{r|c|c|}
    \cline{2-3}
\textcolor{red}{x} & x^2 & 6x \\
    \cline{2-3}
\textcolor{red}{+2} & 2x & 12 \\
    \cline{2-3}
    \end{block}
\end{blockarray}
$
\end{document}

结果和以前一样。

Answer 2

带包裹nicematrix。

\documentclass{article}
\usepackage{nicematrix}
\usepackage{xcolor}

\begin{document}

\renewcommand\arraystretch{1.8}
$\begin{NiceMatrix}%
  [
    hvlines,
    columns-width=auto,
    first-row, code-for-first-row = \color{red},
    first-col, code-for-first-col = \color{red}
  ]
   & x   & +6 \\
x  & x^2 & 6x \\
+2 & 2x  & 12
\end{NiceMatrix}$

\end{document}

您需要多次编译（因为nicematrix使用 PGF/Tikz 节点）。