创建可重复使用的 tikz 图形模板

Question 1

您可以使用\tikzset和\newcommand创建通用代码放入您的.cls文件中。

例如我创建了：

myblue可以代替“非常厚，蓝色”的样式
myhelp帮助行命令
awhitepoint和bluepoint pics 代表圆圈（填充白色或蓝色，您也可以创建一个带有pic参数的唯一圆圈来传递颜色选项）
mylabels添加标签的命令。

查看代码以了解如何使用它们：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,shapes.symbols,positioning,decorations.pathmorphing}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% you may put a code like this in your .cls file
\tikzset{%
    myblue/.style={blue, very thick},
    pics/bluepoint/.style={code={%          
        \draw[very thick, blue, fill] (0,0) circle [radius=.08];
    }},
    pics/whitepoint/.style={code={%         
        \draw[very thick, blue, fill=white] (0,0) circle [radius = .08];
    }},
    }
\newcommand{\myhelp}{\draw[help lines] (\xmin, \ymin) grid (\xmax, \ymax);}
\newcommand{\mylabels}{%
    \foreach \x in {1} \draw (0,\x)node[right]{\x};
    \foreach \x in {1} \draw (\x,0)node[below]{\x};}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
\begin{tikzpicture}[scale=.9]
  \def \xmin {-3}
  \def \xmax {3}
  \def \ymin {-2}
  \def \ymax {3}
  \myhelp  
  \draw [<->] (\xmin-.3,0) -- (\xmax+.3,0);
  \draw [<->] (0,\ymin-.3) -- (0,\ymax+.3);
  \node at (0,\ymax + .6) {$g(x)$};
  \node at (\xmax + .6,0) {$x$};
  \node at (-2, 1.5) {$y = g(x)$};
  \draw[domain=-1.828:1, myblue, smooth] plot
    ({\x}, {-0.5*(\x-1)^2 + 2});
  \draw[domain=1:2.732, myblue, smooth] plot
      ({\x}, {-1*(\x-1)^2 + 1});
  \pic at (1,1) {bluepoint};
  \pic at (1,2) {whitepoint};
  \mylabels
\end{tikzpicture}
\end{document}

当然输出是完全相同的：

如果它有用，这是带有箭头尖端颜色参数选项的版本，默认blue值为：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,shapes.symbols,positioning,decorations.pathmorphing}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% you may put a code like this in your .cls file
\tikzset{%
    myblue/.style={blue, very thick},
    pics/mypoint/.style={code={%          
            \draw[very thick, blue, fill=#1] (0,0) circle [radius=.08];
    }},
    pics/mypoint/.default=blue
}
\newcommand{\myhelp}{\draw[help lines] (\xmin, \ymin) grid (\xmax, \ymax);}
\newcommand{\mylabels}{%
    \foreach \x in {1} \draw (0,\x)node[right]{\x};
    \foreach \x in {1} \draw (\x,0)node[below]{\x};}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
    \begin{tikzpicture}[scale=.9]
    \def \xmin {-3}
    \def \xmax {3}
    \def \ymin {-2}
    \def \ymax {3}
    \myhelp  
    \draw [<->] (\xmin-.3,0) -- (\xmax+.3,0);
    \draw [<->] (0,\ymin-.3) -- (0,\ymax+.3);
    \node at (0,\ymax + .6) {$g(x)$};
    \node at (\xmax + .6,0) {$x$};
    \node at (-2, 1.5) {$y = g(x)$};
    \draw[domain=-1.828:1, myblue, smooth] plot
    ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, myblue, smooth] plot
    ({\x}, {-1*(\x-1)^2 + 1});
    \pic at (1,1) {mypoint};
    \pic at (1,2) {mypoint=white};
    \mylabels
    \end{tikzpicture}
\end{document}

Answer

您可以使用\tikzset和\newcommand创建通用代码放入您的.cls文件中。

例如我创建了：

myblue可以代替“非常厚，蓝色”的样式
myhelp帮助行命令
awhitepoint和bluepoint pics 代表圆圈（填充白色或蓝色，您也可以创建一个带有pic参数的唯一圆圈来传递颜色选项）
mylabels添加标签的命令。

查看代码以了解如何使用它们：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,shapes.symbols,positioning,decorations.pathmorphing}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% you may put a code like this in your .cls file
\tikzset{%
    myblue/.style={blue, very thick},
    pics/bluepoint/.style={code={%          
        \draw[very thick, blue, fill] (0,0) circle [radius=.08];
    }},
    pics/whitepoint/.style={code={%         
        \draw[very thick, blue, fill=white] (0,0) circle [radius = .08];
    }},
    }
\newcommand{\myhelp}{\draw[help lines] (\xmin, \ymin) grid (\xmax, \ymax);}
\newcommand{\mylabels}{%
    \foreach \x in {1} \draw (0,\x)node[right]{\x};
    \foreach \x in {1} \draw (\x,0)node[below]{\x};}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
\begin{tikzpicture}[scale=.9]
  \def \xmin {-3}
  \def \xmax {3}
  \def \ymin {-2}
  \def \ymax {3}
  \myhelp  
  \draw [<->] (\xmin-.3,0) -- (\xmax+.3,0);
  \draw [<->] (0,\ymin-.3) -- (0,\ymax+.3);
  \node at (0,\ymax + .6) {$g(x)$};
  \node at (\xmax + .6,0) {$x$};
  \node at (-2, 1.5) {$y = g(x)$};
  \draw[domain=-1.828:1, myblue, smooth] plot
    ({\x}, {-0.5*(\x-1)^2 + 2});
  \draw[domain=1:2.732, myblue, smooth] plot
      ({\x}, {-1*(\x-1)^2 + 1});
  \pic at (1,1) {bluepoint};
  \pic at (1,2) {whitepoint};
  \mylabels
\end{tikzpicture}
\end{document}

当然输出是完全相同的：

如果它有用，这是带有箭头尖端颜色参数选项的版本，默认blue值为：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,shapes.symbols,positioning,decorations.pathmorphing}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% you may put a code like this in your .cls file
\tikzset{%
    myblue/.style={blue, very thick},
    pics/mypoint/.style={code={%          
            \draw[very thick, blue, fill=#1] (0,0) circle [radius=.08];
    }},
    pics/mypoint/.default=blue
}
\newcommand{\myhelp}{\draw[help lines] (\xmin, \ymin) grid (\xmax, \ymax);}
\newcommand{\mylabels}{%
    \foreach \x in {1} \draw (0,\x)node[right]{\x};
    \foreach \x in {1} \draw (\x,0)node[below]{\x};}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
    \begin{tikzpicture}[scale=.9]
    \def \xmin {-3}
    \def \xmax {3}
    \def \ymin {-2}
    \def \ymax {3}
    \myhelp  
    \draw [<->] (\xmin-.3,0) -- (\xmax+.3,0);
    \draw [<->] (0,\ymin-.3) -- (0,\ymax+.3);
    \node at (0,\ymax + .6) {$g(x)$};
    \node at (\xmax + .6,0) {$x$};
    \node at (-2, 1.5) {$y = g(x)$};
    \draw[domain=-1.828:1, myblue, smooth] plot
    ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, myblue, smooth] plot
    ({\x}, {-1*(\x-1)^2 + 1});
    \pic at (1,1) {mypoint};
    \pic at (1,2) {mypoint=white};
    \mylabels
    \end{tikzpicture}
\end{document}

Question 2

一种方法是使用\pgfkeys存储图表的各种默认值，然后将所有内容包装在自定义环境中，并通过键值对提供新设置。例如，代码

\pgfkeys{/mygraph/.is family, /mygraph,
  xmin/.initial = -3, % defaults for xmin, xmax, ymin,ymax
  xmax/.initial =  3,
  ymin/.initial = -3,
  ymax/.initial =  3,
  ylabel/.initial = f(x),% default function name
  scale/.initial = 0.9,  % tikzpicture scale
  xtics/.initial = {1}, % list of marked coordinates on x-axis
  ytics/.initial = {1},  % list of marked coordinates on y-axis
}

设置 x 和 y 值的最大和最小值的初始值（或默认值）、y 轴的标签和刻度。然后，您可以定义一个环境，例如，MyGraph该环境采用可选参数，该参数传递给\pgfkeysvia \pgfkeys{/mygraph, #1}以更改这些设置。这将用作

\begin{MyGraph}[ylabel=g(x)]
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, {Circle[open, fill=white]}-] plot ({\x}, {-1*(\x-1)^2 + 1});
\end{MyGraph}

这将绘制问题中的图形！特别注意\usetikzlibrary{arrows.meta}提供圆形“箭头”头。一般来说，MyGraph环境的“内容”将是特定于图形的材料。

环境MyGraph将打开tikzpicture环境并绘制“初始代码”。以下是一个可能的定义：

\newenvironment{Mygraph}[1][]%
   {\pgfkeys{/mygraph, #1}% process settings
    \begin{tikzpicture}[scale=\Gval{scale},
                        draw/.append style={very thick, blue}]
      \draw[help lines](\Gval{xmin},\Gval{ymin}) grid (\Gval{xmax},\Gval{ymax});
      \draw[thin, black] [<->] (\Gval{xmin}-0.3,0) -- (\Gval{xmax}+0.3,0);
      \draw[thin, black] [<->] (0,\Gval{ymin}-0.3) -- (0,\Gval{ymax}+0.3);
      \node at (0,\Gval{ymax} + .6) {$\Gval{ylabel}$};
      \node at (\Gval{xmax} + .6,0) {$x$};
      \node at (-2, 1.5) {$y = \Gval{ylabel}$};
    }
    {\end{tikzpicture}}

（\Gval宏是的快捷方式\pgfkeysvalueof{/mygraph/#1}，用于提取相应键的值。）

注意环境draw/.append style={very thick, blue}开始时的tikzpicture：这会将粗蓝线设置为\draw命令的默认值。这样做有一个小缺点，因为现在需要\draw[black]....在 x 和 y 轴上书写标签。另一种方法是使用 \tikzset来定义样式：

\tikzset{% define styles for commonly used elements
  myline/.style={very thick, blue}
}

\draw[myline]...之后，当您想要粗蓝线时，可以使用。使用\tikzset更明确，因此可能更好，但如果您希望“几乎所有”绘图命令都给出粗蓝线，这将为您节省一些输入。

MyGraph下面是使用环境绘制两个“不同”图形的完整 MWE ：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}

% Using pgfkeys makes it easier to use key-value settings for the graph
\pgfkeys{/mygraph/.is family, /mygraph,
  xmin/.initial = -3,    % defaults for xmin, xmax, ymin,ymax
  xmax/.initial =  3,
  ymin/.initial = -3,
  ymax/.initial =  3,
  ylabel/.initial = f(x),% default function name
  scale/.initial = 0.9,  % tikzpicture scale
  xtics/.initial = {1},  % list of marked coordinates on x-axis
  ytics/.initial = {1},   % list of marked coordinates on y-axis
}

% shortcut to access values of /mygraph
\newcommand\Gval[1]{\pgfkeysvalueof{/mygraph/#1}}

% graph environment with optional argument for changing defaults
\newenvironment{Mygraph}[1][]%
   {\pgfkeys{/mygraph, #1}% process settings
    \begin{tikzpicture}[scale=\Gval{scale},
                        draw/.append style={very thick, blue}]
      \draw[help lines](\Gval{xmin},\Gval{ymin}) grid (\Gval{xmax},\Gval{ymax});
      \draw[thin, black] [<->] (\Gval{xmin}-0.3,0) -- (\Gval{xmax}+0.3,0);
      \draw[thin, black] [<->] (0,\Gval{ymin}-0.3) -- (0,\Gval{ymax}+0.3);
      \node at (0,\Gval{ymax} + .6) {$\Gval{ylabel}$};
      \node at (\Gval{xmax} + .6,0) {$x$};
      \node at (-2, 1.5) {$y = \Gval{ylabel}$};
      \xdef\xtics{\Gval{xtics}}% for reasons unknown can't use this directly
      \foreach \x in \xtics { \draw[black](\x,0)node[below]{\small$\x$}; }
      \xdef\ytics{\Gval{ytics}}
      \foreach \y in \ytics { \draw[black](0,\y)node[left]{\small$\y$}; }
    }
    {\end{tikzpicture}}

\begin{document}

  \begin{Mygraph}
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, -{Circle[open, fill=white]}] plot ({\x}, {-1*(\x-1)^2 + 1});
  \end{Mygraph}

  \begin{Mygraph}[ylabel=g(x), xmin=-4, xmax=4, scale=0.5, xtics={1,2,3}, ytics={1,3}]
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, {Circle[open,fill=white]}-] plot ({\x}, {-1*(\x-1)^2 + 1});
  \end{Mygraph}

\end{document}

输出如下：

当然，您可以添加更多设置来\pgfkeys{/mygraph/,...}进一步自定义图表。例如，您可能希望对轴上的标记 x 和 y 值以及标签的位置y=g(x)等执行此操作。您还可以做许多其他事情\pgfkeys——请参阅蒂克兹手册以了解更多信息。

Answer

一种方法是使用\pgfkeys存储图表的各种默认值，然后将所有内容包装在自定义环境中，并通过键值对提供新设置。例如，代码

\pgfkeys{/mygraph/.is family, /mygraph,
  xmin/.initial = -3, % defaults for xmin, xmax, ymin,ymax
  xmax/.initial =  3,
  ymin/.initial = -3,
  ymax/.initial =  3,
  ylabel/.initial = f(x),% default function name
  scale/.initial = 0.9,  % tikzpicture scale
  xtics/.initial = {1}, % list of marked coordinates on x-axis
  ytics/.initial = {1},  % list of marked coordinates on y-axis
}

设置 x 和 y 值的最大和最小值的初始值（或默认值）、y 轴的标签和刻度。然后，您可以定义一个环境，例如，MyGraph该环境采用可选参数，该参数传递给\pgfkeysvia \pgfkeys{/mygraph, #1}以更改这些设置。这将用作

\begin{MyGraph}[ylabel=g(x)]
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, {Circle[open, fill=white]}-] plot ({\x}, {-1*(\x-1)^2 + 1});
\end{MyGraph}

这将绘制问题中的图形！特别注意\usetikzlibrary{arrows.meta}提供圆形“箭头”头。一般来说，MyGraph环境的“内容”将是特定于图形的材料。

环境MyGraph将打开tikzpicture环境并绘制“初始代码”。以下是一个可能的定义：

\newenvironment{Mygraph}[1][]%
   {\pgfkeys{/mygraph, #1}% process settings
    \begin{tikzpicture}[scale=\Gval{scale},
                        draw/.append style={very thick, blue}]
      \draw[help lines](\Gval{xmin},\Gval{ymin}) grid (\Gval{xmax},\Gval{ymax});
      \draw[thin, black] [<->] (\Gval{xmin}-0.3,0) -- (\Gval{xmax}+0.3,0);
      \draw[thin, black] [<->] (0,\Gval{ymin}-0.3) -- (0,\Gval{ymax}+0.3);
      \node at (0,\Gval{ymax} + .6) {$\Gval{ylabel}$};
      \node at (\Gval{xmax} + .6,0) {$x$};
      \node at (-2, 1.5) {$y = \Gval{ylabel}$};
    }
    {\end{tikzpicture}}

（\Gval宏是的快捷方式\pgfkeysvalueof{/mygraph/#1}，用于提取相应键的值。）

注意环境draw/.append style={very thick, blue}开始时的tikzpicture：这会将粗蓝线设置为\draw命令的默认值。这样做有一个小缺点，因为现在需要\draw[black]....在 x 和 y 轴上书写标签。另一种方法是使用 \tikzset来定义样式：

\tikzset{% define styles for commonly used elements
  myline/.style={very thick, blue}
}

\draw[myline]...之后，当您想要粗蓝线时，可以使用。使用\tikzset更明确，因此可能更好，但如果您希望“几乎所有”绘图命令都给出粗蓝线，这将为您节省一些输入。

MyGraph下面是使用环境绘制两个“不同”图形的完整 MWE ：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}

% Using pgfkeys makes it easier to use key-value settings for the graph
\pgfkeys{/mygraph/.is family, /mygraph,
  xmin/.initial = -3,    % defaults for xmin, xmax, ymin,ymax
  xmax/.initial =  3,
  ymin/.initial = -3,
  ymax/.initial =  3,
  ylabel/.initial = f(x),% default function name
  scale/.initial = 0.9,  % tikzpicture scale
  xtics/.initial = {1},  % list of marked coordinates on x-axis
  ytics/.initial = {1},   % list of marked coordinates on y-axis
}

% shortcut to access values of /mygraph
\newcommand\Gval[1]{\pgfkeysvalueof{/mygraph/#1}}

% graph environment with optional argument for changing defaults
\newenvironment{Mygraph}[1][]%
   {\pgfkeys{/mygraph, #1}% process settings
    \begin{tikzpicture}[scale=\Gval{scale},
                        draw/.append style={very thick, blue}]
      \draw[help lines](\Gval{xmin},\Gval{ymin}) grid (\Gval{xmax},\Gval{ymax});
      \draw[thin, black] [<->] (\Gval{xmin}-0.3,0) -- (\Gval{xmax}+0.3,0);
      \draw[thin, black] [<->] (0,\Gval{ymin}-0.3) -- (0,\Gval{ymax}+0.3);
      \node at (0,\Gval{ymax} + .6) {$\Gval{ylabel}$};
      \node at (\Gval{xmax} + .6,0) {$x$};
      \node at (-2, 1.5) {$y = \Gval{ylabel}$};
      \xdef\xtics{\Gval{xtics}}% for reasons unknown can't use this directly
      \foreach \x in \xtics { \draw[black](\x,0)node[below]{\small$\x$}; }
      \xdef\ytics{\Gval{ytics}}
      \foreach \y in \ytics { \draw[black](0,\y)node[left]{\small$\y$}; }
    }
    {\end{tikzpicture}}

\begin{document}

  \begin{Mygraph}
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, -{Circle[open, fill=white]}] plot ({\x}, {-1*(\x-1)^2 + 1});
  \end{Mygraph}

  \begin{Mygraph}[ylabel=g(x), xmin=-4, xmax=4, scale=0.5, xtics={1,2,3}, ytics={1,3}]
    \draw[domain=-1.828:1, smooth,-{Circle[blue]}] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth, {Circle[open,fill=white]}-] plot ({\x}, {-1*(\x-1)^2 + 1});
  \end{Mygraph}

\end{document}

输出如下：

当然，您可以添加更多设置来\pgfkeys{/mygraph/,...}进一步自定义图表。例如，您可能希望对轴上的标记 x 和 y 值以及标签的位置y=g(x)等执行此操作。您还可以做许多其他事情\pgfkeys——请参阅蒂克兹手册以了解更多信息。

Question 3

@andrew 和 @CarLaTeX 的上述回答具有建设性和指导意义。我采纳了他们两个答案的部分内容，得出了以下代码。

在我的班级档案中，我有添加以下内容，已经有大量（不相关的）代码。我不想在这里发布整个内容，因此相关部分如下：

% This is the setup for the wcgraph environment below
\tikzset{%
    myblue/.style={blue, very thick},
    pics/closed/.style={code={%
            \draw[very thick, blue, fill] (0,0) circle [radius=.08];
    }},
    pics/open/.style={code={%
            \draw[very thick, blue, fill=white] (0,0) circle [radius=.08];
    }},
    pics/mypoint/.default=blue,
    draw/.append style={very thick, blue},
    >=latex,
    >=stealth,
}

% This is the setup for the wcgraph environment below
\pgfkeys{/mygraph/.is family, /mygraph,
  xmin/.initial = -3,         % defaults for xmin, xmax, ymin,ymax
  xmax/.initial =  3,
  ymin/.initial = -3,
  ymax/.initial =  3,
  ylabel/.initial = f(x),     % default function name
  xlabel/.initial = x,        % default independent variable
  scale/.initial = 0.9,       % tikzpicture scale
  xtics/.initial = {1},       % list of marked coordinates on x-axis
  ytics/.initial = {1},       % list of marked coordinates on y-axis
  xticsloc/.initial = below,  % default location for tick labels
  yticsloc/.initial = left,
  helplines/.initial = draw,  % Default to draw the help lines
}

% A new command to grab values from pgfkeys above
\newcommand\getVal[1]{\pgfkeysvalueof{/mygraph/#1}}

% A command to draw helplines. To not draw them, pass the option "hide"
\newcommand{\helplines}[1]{
  \ifthenelse{\equal{#1}{draw}}{
    \draw[help lines] (\getVal{xmin},\getVal{ymin}) grid (\getVal{xmax},\getVal{ymax});
  }{}
}

% The graph environment with optional arguments for changing defaults
\newenvironment{wcgraph}[1][]%
   {\pgfkeys{/mygraph, #1}% process settings
    \begin{tikzpicture}[scale=\getVal{scale}]
      \helplines{\getVal{helplines}}
      \draw[thin, black] [->] (\getVal{xmin}-0.3,0) -- (\getVal{xmax}+0.3,0);
      \draw[thin, black] [->] (0,\getVal{ymin}-0.3) -- (0,\getVal{ymax}+0.3);
      \node at (0,\getVal{ymax} + .6) {$\getVal{ylabel}$};
      \node at (\getVal{xmax} + .6,0) {$\getVal{xlabel}$};
      \xdef\xtics{\getVal{xtics}} % Can't use this directly for some reason
      \foreach \x in \xtics {
        \draw[black](\x,0)node[\getVal{xticsloc}]{\small$\x$};
      }
      \foreach \x in {\getVal{xmin},...,\getVal{xmax}}{
        \draw[black, thin, shift={(\x,0)}] (0pt,1pt) -- (0pt,-1pt);
      }
      \xdef\ytics{\getVal{ytics}}
      \foreach \y in \ytics {
        \draw[black](0,\y)node[left]{\small$\y$};
      }
      \foreach \y in {\getVal{ymin},...,\getVal{ymax}}{
        \draw[black, thin, shift={(0,\y)}] (1pt,0pt) -- (-1pt,0pt);
      }
    }
    {\end{tikzpicture}}

在我的.tex文件中，我使用的worksheet.cls类（如上所述）包含了很多其他内容，而不是我直接在上面发布的内容。 MWE 是：

\documentclass{worksheet}

\begin{document}

  \begin{wcgraph}[xmin=-2, ymin=-2]
    \draw[domain=-1.828:1, smooth] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth] plot ({\x}, {-1*(\x-1)^2 + 1});
    \pic at (1,2) {open};
    \pic at (1,1) {closed};
  \end{wcgraph}

  \begin{wcgraph}[helplines=hide, xmin=-2, ymin=-2, scale=1.8]
    \draw[domain=-1.828:1, smooth] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth] plot ({\x}, {-1*(\x-1)^2 + 1});
    \pic at (1,2) {open};
    \pic at (1,1) {closed};
  \end{wcgraph}

\end{document}

生成以下图表：

也许这里不是提出后续问题的地方（如果有人建议，我很乐意编辑此内容并发布另一个问题），但我想稍微扩展一下。我认为这与原始问题高度相关，因此进行了后续讨论。我想添加一个命令，通过指定坐标来绘制所需的所有“打开”节点。我在新命令中传递坐标“列表”时遇到问题。我想使用\foreachon #1，即我的新命令的参数。这没有按我预期的方式工作，并且它不会解析为坐标。我已经阅读了 PGF 指南和大量帖子，\foreach但都没有成功。

我想使用以下代码来绘制上述图表：

  \begin{wcgraph}[helplines=hide, xmin=-2, ymin=-2, scale=1.8]
    \draw[domain=-1.828:1, smooth] plot ({\x}, {-0.5*(\x-1)^2 + 2});
    \draw[domain=1:2.732, smooth] plot ({\x}, {-1*(\x-1)^2 + 1});
    \openpics{(1,2)};
    \closedpics{(1,1)};
  \end{wcgraph}

当我有更复杂的图表时，这将会带来很大的好处。

我对这个新命令的最佳猜测（将添加到我的.cls文件中）：

% A new command to draw all open pics I need.
\newcommand{\openpics}[1]{
  \foreach \coord in {#1}{
    \pic at \coord {open};
  }
}

并且\closedpics命令也类似。

Answer