将刻度标签移至比“左下方”和“右下方”更近的位置

Question

我有一条抛物线及其对称轴的图。在x轴上x标有截距。如何将标签移近刻度线？

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{amsfonts}

\usepackage{tikz}
\usetikzlibrary{calc}

\usepackage{pgfplots}
\pgfplotsset{compat=1.11}


\begin{document}

\begin{tikzpicture}

\begin{axis}[width=2.5in, height=2.5in, axis lines=middle, clip=false,
    axis lines=middle, clip=false,
    xmin=-7.56,xmax=23.56,
    ymin=-150,ymax=150,
    restrict y to domain=-150:150,
    xtick={-3},
    xticklabel style={font=\tiny, below left},
    xticklabels={\makebox[0pt][r]{$-$}$3$},
    extra x ticks={19},
    extra x tick style={font=\tiny, xticklabel style={below right}},
    extra x tick labels={19},
    ytick={\empty},
    axis line style={latex-latex},
    xlabel=\textit{x}, ylabel=\textit{y},
    axis line style={shorten >=-7.5pt, shorten <=-7.5pt},
    xlabel style={at={(ticklabel* cs:1)}, xshift=7.5pt, anchor=north west},
    ylabel style={at={(ticklabel* cs:1)}, yshift=7.5pt, anchor=south west}
]


%The parabola y = x^{2} - 16x - 57 is drawn over the interval [8-11*sqrt(2), 8+11*sqrt(2)].
%Its x-intercepts are (-3,0) and (19,0), and its vertex is (8,-121).
\addplot[domain={8-11*sqrt(2)}:{8+11*sqrt(2)}] {x^2 - 16*x - 57};

%The axis of symmetry is drawn.
\addplot[dashed, latex-latex, domain=-140:140] (8,x) node[pos=0.2, anchor=south, font=\scriptsize, sloped]{$x=8$};

\end{axis}

\end{tikzpicture}

\end{document}

Answer 1

如果添加draw到xticklabel style，您会看到节点文本和边框之间有一些填充，这是inner sep（默认 0.333em）：

通过向相关样式inner sep添加（或其他值）来减少，将实现您的要求。以下是零内部 sep：inner sep=0pt

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{amsfonts}

\usepackage{tikz}
\usetikzlibrary{calc}

\usepackage{pgfplots}
\pgfplotsset{compat=1.11}


\begin{document}

\begin{tikzpicture}

\begin{axis}[width=2.5in, height=2.5in, axis lines=middle, clip=false,
    axis lines=middle, clip=false,
    xmin=-7.56,xmax=23.56,
    ymin=-150,ymax=150,
    restrict y to domain=-150:150,
    xtick={-3},
    xticklabel style={font=\tiny, inner sep=0pt, below left},
    xticklabels={\makebox[0pt][r]{$-$}$3$},
    extra x ticks={19},
    extra x tick style={font=\tiny, xticklabel style={below right}},
    extra x tick labels={19},
    ytick={\empty},
    axis line style={latex-latex},
    xlabel=\textit{x}, ylabel=\textit{y},
    axis line style={shorten >=-7.5pt, shorten <=-7.5pt},
    xlabel style={at={(ticklabel* cs:1)}, xshift=7.5pt, anchor=north west},
    ylabel style={at={(ticklabel* cs:1)}, yshift=7.5pt, anchor=south west}
]


%The parabola y = x^{2} - 16x - 57 is drawn over the interval [8-11*sqrt(2), 8+11*sqrt(2)].
%Its x-intercepts are (-3,0) and (19,0), and its vertex is (8,-121).
\addplot[domain={8-11*sqrt(2)}:{8+11*sqrt(2)}] {x^2 - 16*x - 57};

%The axis of symmetry is drawn.
\addplot[dashed, latex-latex, domain=-140:140] (8,x) node[pos=0.2, anchor=south, font=\scriptsize, sloped]{$x=8$};

\end{axis}

\end{tikzpicture}
\end{document}

Answer 2

移动标签的另一种方法（以防它们干扰其他元素）是在below left或之后添加一些距离below right。编辑除非与库一起使用，否则此选项已弃用positioning。（非常感谢 Torbjørn T.！）

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{amsfonts}

\usepackage{tikz}
\usetikzlibrary{calc,positioning}

\usepackage{pgfplots}
\pgfplotsset{compat=1.11}


\begin{document}

\begin{tikzpicture}

\begin{axis}[width=2.5in, height=2.5in, axis lines=middle, clip=false,
    axis lines=middle, clip=false,
    xmin=-7.56,xmax=23.56,
    ymin=-150,ymax=150,
    restrict y to domain=-150:150,
    xtick={-3},
    xticklabel style={font=\tiny, below left=-0.4em},
    xticklabels={\makebox[0pt][r]{$-$}$3$},
    extra x ticks={19},
    extra x tick style={font=\tiny, xticklabel style={below right=-0.4em}},
    extra x tick labels={19},
    ytick={\empty},
    axis line style={latex-latex},
    xlabel=\textit{x}, ylabel=\textit{y},
    axis line style={shorten >=-7.5pt, shorten <=-7.5pt},
    xlabel style={at={(ticklabel* cs:1)}, xshift=7.5pt, anchor=north west},
    ylabel style={at={(ticklabel* cs:1)}, yshift=7.5pt, anchor=south west}
]


%The parabola y = x^{2} - 16x - 57 is drawn over the interval [8-11*sqrt(2), 8+11*sqrt(2)].
%Its x-intercepts are (-3,0) and (19,0), and its vertex is (8,-121).
\addplot[domain={8-11*sqrt(2)}:{8+11*sqrt(2)}] {x^2 - 16*x - 57};

%The axis of symmetry is drawn.
\addplot[dashed, latex-latex, domain=-140:140] (8,x) node[pos=0.2, anchor=south, font=\scriptsize, sloped]{$x=8$};

\end{axis}

\end{tikzpicture}

\end{document}