pgfplot 环境中的符号刻度

Question

我有以下代码：

\begin{tikzpicture}
    \begin{axis}[axis lines = left, xlabel={$x$}, ylabel={$E$}, yticklabels=\empty, xticklabels=\empty, axis lines=middle, xmax=1.2, ymax=1.2, legend pos=north west,
    %symbolic x coords={-A,A},
    %xmin = {-A},
    %xmax = {A},
    %xtickmax={2},
    ]
    \addplot[
    domain=-1:1, 
    samples=100, color=red,
    dashed,
    ]
    {-x^2+1};
    \addlegendentry{$T(x)$}
    
    \addplot[
    domain=-1:1, 
    samples=100,
    ]
    {x^2};
    \addlegendentry{$U(x)$}
    \end{axis}
\end{tikzpicture}

我试图强制刻度在点 (-1/sqrt(2),0) 和 (0,1/sqrt(2)) 处为 (-A,0) 和 (A,0)。有人能帮我实现这个吗？

Answer 1

目前还不完全清楚您的问题是否只是 xtick 标签，或者您希望重现显示的图像。假设第一种可能性：

\documentclass[border=3.141592]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}

\begin{document}
    \begin{tikzpicture}
\begin{axis}[
    axis lines=center, 
    xlabel={$x$}, ylabel={$E$}, 
    ytick=\empty, 
    xtick = {-1,1},
    xticklabels={-A,A},
    extra x ticks={0},
    extra x tick labels={0},    
    xmax=1.2, ymax=1.2, 
    legend pos=north west,
    domain=-1:1,
    samples=100,
    ]
    \addplot[color=red,dashed]  {-x^2+1};
    \addlegendentry{$T(x)$}

    \addplot[no marks] {x^2};
    \addlegendentry{$U(x)$}
    \end{axis}
\end{tikzpicture}
\end{document}