如何仅对重叠抛物线的一部分进行着色

Question

我想对朝上的抛物线进行阴影处理，但只处理两者不相交的区域，即 (0,-2) 到 (0,2) 的区域。

\documentclass[fleqn]{article}
\usepackage{tikz}
\usetikzlibrary{arrows,backgrounds,snakes}
\usepackage{pgfplots}
\usepgfplotslibrary{fillbetween}
\begin{document}
\begin{tikzpicture}
        \begin{axis}[
                samples=1000,
                xlabel=$x$,
                ylabel=$y$,
            xmin=-4.5,xmax=4.5,
                ymin=-4.5,ymax=4.5,
            grid=both,
                grid style={line width=.01pt, draw=black!25},
            major grid style={line width=.1pt},
                axis lines=middle,
            x label style={at={(current axis.right of origin)},anchor=north, below=-5mm},
            minor x tick num=3,
            minor y tick num=3,
            ticklabel style={font=\small},
            enlargelimits={abs=0.5},
                ]
            \addplot[smooth,domain = -6:6,name path = A]{x^2-2};
            \addplot[smooth,domain = -6:6,name path = B]{2-x^2};
            \addplot[draw=none,name path = C]{6};
            \addplot[gray,opacity=0.2] fill between[of=A and C,soft clip={domain=-10:10}];
        \end{axis}
    \end{tikzpicture}
\end{document}

这是我目前拥有的代码。

Answer 1

对于仅对抛物线重叠部分进行阴影处理，您可以使用选项split和every even segment/.style={...}：

梅威瑟：

\documentclass[fleqn]{article}
\usepackage{pgfplots}       % it load tikz too
\pgfplotsset{compat=1.17}   % it is very recommended to be added
\usepgfplotslibrary{fillbetween}
\usetikzlibrary{arrows,
                backgrounds,
                decorations.pathmorphing,
                % snakes is part of decorations.pathmorphing 
                }
\begin{document}
    \begin{tikzpicture}
\begin{axis}[
    axis lines=middle,
    x label style={anchor=north east},
    xmin=-4.5,  xmax=4.5,   xlabel=$x$,
    ymin=-4.5,  ymax=4.5,   ylabel=$y$,
    grid=both,
    grid style={line width=.1pt},
    major grid style={line width=.1pt, black!75},
    minor x tick num=3,
    minor y tick num=3,
    ticklabel style={font=\small},
    enlargelimits={abs=0.5},
    domain = -6:6, samples=101,
    every axis plot post/.append style={thick}
        ]
    \addplot[name path = A]{x^2-2};
    \addplot[name path = B]{2-x^2};
    \addplot[gray,opacity=0.2] 
        fill between[of=A and B, split,
                     every even segment/.style={fill=none}];
\end{axis}
    \end{tikzpicture}
\end{document}

正如您所注意到的，在上述 MWE 中，与您的相比，进行了以下更改：

• 删除的是加载tikz包，因为它加载了pgfplots
• 添加的是\pgfplotsset
• 过时的snake库被替换为decorations.pathmorphing
• 改变的是x label style
• 改变的是grid style（小网格更加清晰可见）
• 改变的是major grid style（它更加清晰可见）
• 功能固化更厚
• 删除不使用的`\addplot

结果是：

Answer 2

你是这个意思吗：我对 pgf 图不是很熟悉。我只发现你想绘制图 A 和 C 之间的区域。通过将 C 更改为 B，它会绘制函数 A 和 B 之间的区域。然后你只需调整soft clip={domain=< >}。

\documentclass[fleqn]{article}
\usepackage{tikz}
\usetikzlibrary{arrows,backgrounds,snakes}
\usepackage{pgfplots}
\usepgfplotslibrary{fillbetween}
\begin{document}
\begin{tikzpicture}
        \begin{axis}[
                samples=1000,
                xlabel=$x$,
                ylabel=$y$,
            xmin=-4.5,xmax=4.5,
                ymin=-4.5,ymax=4.5,
            grid=both,
                grid style={line width=.01pt, draw=black!25},
            major grid style={line width=.1pt},
                axis lines=middle,
            x label style={at={(current axis.right of origin)},anchor=north, below=-5mm},
            minor x tick num=3,
            minor y tick num=3,
            ticklabel style={font=\small},
            enlargelimits={abs=0.5},
                ]
            \addplot[smooth,domain = -6:6,name path = A]{x^2-2};
            \addplot[smooth,domain = -6:6,name path = B]{2-x^2};
            \addplot[draw=none,name path = C]{6};
            \addplot[gray,opacity=0.2] fill between[of=A and B,soft clip={domain=-1.5:1.5}];
        \end{axis}
    \end{tikzpicture}
\end{document}