PGFPlots：向替代 x 轴添加自定义标签

Question

我有以下情节：

\begin{tikzpicture}
  \begin{semilogxaxis} [
    width=\textwidth,
    height=0.4\textwidth,
    xlabel={Frequency [Hz]},
    ylabel={Volume [dB]},
    xmin=10,
    xmax=10000,
    grid=major,
    smooth,
    legend entries={Trumpet, Trombone, Horn, Tuba},
  ]
    \addplot [blue]             table {recordings/Bb-C4.txt};
    \addplot [orange!50!yellow] table {recordings/C-C4.txt};
    \addplot [green!70!black]   table {recordings/Eb-C4.txt};
    \addplot [red]              table {recordings/F-C4.txt};
  \end{semilogxaxis}
\end{tikzpicture}

这很好，但是虽然在这里描述“频率”很重要，但我还想添加 x 轴刻度和特定频率的标签来表示音符名称。

我感觉我已经接近添加extra x ticks以下选项了semilogxaxis：

    extra x ticks = {262, 523, 784, 1047},                                      
    extra x tick labels={C4,   C5,  G5, C6  },                                  
%    extra x tick style={xticklabel=above}  

但我真的很难理解extra x tick style。这些标签不能干扰正常的 x-tick 标签。答案可能是将它们移动到图的顶部，但将它们移动到轴上方可能是我能做的最好的事情。

使用“两个法令”（如pgfplots 文档) 看起来很接近我想要的，但它只描述了交替的 Y 轴。

---

以下是简化的 MWE：

\documentclass[a4paper,11pt]{book}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\begin{document}


\begin{tikzpicture}
  \begin{semilogxaxis} [
    width=\textwidth,
    height=0.4\textwidth,
    xlabel={Frequency [Hz]},
    ylabel={Volume [dB]},
    xmin=10,
    xmax=10000,
    grid=major,
    smooth,
    extra x ticks = {262, 523, 784, 1047},
    extra x tick labels={C4,   C5,  G5, C6  }
%    extra x tick style={xticklabel=above}
  ]
    \addplot [blue] coordinates {
      (10,-81)
      (102,-93)
      (204,-87)
      (253,-32)
      (301,-67)
      (355,-77)
      (403,-78)
      (452,-81)
      (500,-74)
      (522,-41)
      (554,-77)
      (602,-83)
      (651,-86)
      (705,-87)
      (753,-88)
      (775,-60)
      (780,-52)
      (785,-56)
      (800,-92)
    };
  \end{semilogxaxis}
\end{tikzpicture}

\end{document}

Answer 1

像这样？

\documentclass[twocolumn]{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}
\begin{tikzpicture}
\pgfplotsset{
    width=\textwidth,
    height=0.4\textwidth,
    ylabel={Volume [dB]},
    xmin=10,
    xmax=10000,
    grid=major,
    legend entries={Trumpet, Trombone, Horn, Tuba},
            }
\begin{semilogxaxis} [
    axis x line*=bottom,    % <---
    xlabel={Frequency [Hz]},
                        ]
    \addplot coordinates {
        (10,-81)    (102,-93) (204,-87) (253,-32) (301,-67)
        (355,-77)   (403,-78) (452,-81) (500,-74) (522,-41)
        (554,-77)   (602,-83) (651,-86) (705,-87) (753,-88)
        (775,-60)   (780,-52) (785,-56) (800,-92)
                            };           
\end{semilogxaxis}
\begin{semilogxaxis} [
    axis x line*=top,       % <---
        xtick     = {262, 523, 784, 1047},
        xticklabels = {C4, C5, G5, C6}  
                        ]
    \addplot coordinates {
        (10,-81)    (102,-93) (204,-87) (253,-32) (301,-67)
        (355,-77)   (403,-78) (452,-81) (500,-74) (522,-41)
        (554,-77)   (602,-83) (651,-86) (705,-87) (753,-88)
        (775,-60)   (780,-52) (785,-56) (800,-92)
                            };
\end{semilogxaxis}
\end{tikzpicture}
\end{document}

编辑(1)： 现在向第二个axis添加了选项axis y line =none,。这应该允许ytick仅在第一个axis环境中写入。

抱歉，但我可以用你的真实数据测试其效果（它们仍然未知），因此为了测试，我对第二个坐标进行了微小的变化axis。

编辑（2）：
添加\pgfplotsset了axisOP 在下面的评论中建议的选项。

\documentclass[twocolumn]{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}
\begin{tikzpicture}
\pgfplotsset{
    width=\textwidth,
    height=0.4\textwidth,
    grid=major,
    scale only axis,        % <--- added
    xmin=10,    xmax=10000,
    ymin=-100,  ymax=-20,   % <--- added
    ylabel={Volume [dB]},
    no marks,               % <--- added 
every axis plot post/.append style={thick},
    legend entries={Trumpet, Trombone, Horn, Tuba},
            }
\begin{semilogxaxis} [
    axis x line*=bottom,   
    xlabel={Frequency [Hz]},
                        ]
    \addplot coordinates {
        (10,-81)    (102,-93) (204,-87) (253,-32) (301,-67)
        (355,-77)   (403,-78) (452,-81) (500,-74) (522,-41)
        (554,-77)   (602,-83) (651,-86) (705,-87) (753,-88)
        (775,-60)   (780,-52) (785,-56) (800,-92)
                            };           
\end{semilogxaxis}
\begin{semilogxaxis} [
    axis x line*=top,       
    axis y line =none,      % <--- added
        xtick     = {262, 523, 784, 1047},
        xticklabels = {C4, C5, G5, C6}  
                        ]
\addplot +[red] coordinates {   % <--- changed coordinates   
        (10,-51)    (102,-83) (204,-77) (253,-42) (301,-37)
        (355,-87)   (403,-78) (452,-71) (500,-74) (522,-33)
        (554,-55)   (602,-88) (651,-86) (705,-87) (753,-78)
        (775,-54)   (780,-56) (785,-65) (800,-88)
                            };
\end{semilogxaxis}
\end{tikzpicture}
\end{document}