如何使用 pi 标记窦的轴？

Question

我正在使用 pgfplot 绘制正弦函数，并希望使用 pi 的倍数（pi/4、pi/2、2*pi……）标记 x 轴的刻度，因为它们是研究正弦函数时要可视化的“重要”x 值。

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.14}
\begin{document}

\begin{tikzpicture}

\begin{axis}[domain=0:2*pi, ymax=1.2, samples=100, grid=major,
  xlabel=$\alpha$, ylabel=$sin(\alpha)$, 
  xtick = {0,1,...,6}, ytick = {-1,-0.5,...,1}] %I assume this the part that I need to change?
    \addplot [blue](\x, {sin(\x r)});
\end{axis}

\end{tikzpicture}
\end{document}

我尝试在上面代码中 % 附近的括号中给出 pi 的常规值，但使用“pi”或“\pi”都没有用。我是不是漏掉了什么？使用上面的代码绘制的图如下所示：

Answer 1

一个（简单的）替代方案：

• 绘图sin(x)（以度为单位）

• 标签勾选0，，\frac{\pi}{4}....

  \documentclass[margin=3mm]{standalone}
  \usepackage{pgfplots}
  \pgfplotsset{compat=1.14}
  
  \begin{document}
      \begin{tikzpicture}
  \begin{axis}[
         grid,
         ymax = 1.2,
       xlabel = $\alpha$, ylabel=$\sin(\alpha)$,
        xtick = {0,45,...,360},
  xticklabels = {\mathstrut 0,
                  $\frac{ \pi}{4}$,$\frac{ \pi}{2}$,$\frac{3\pi}{4}$,$\mathstrut \pi$,
                  $\frac{5\pi}{4}$,$\frac{3\pi}{2}$,$\frac{7\pi}{4}$,$\mathstrut2\pi$},
       domain = 0:360,
      samples = 73,
      no marks
                  ]
      \addplot +[very thick] {sin(x)};
  \end{axis}
      \end{tikzpicture}
  \end{document}
  

Answer 2

欢迎来到 TeX.SE！这里有一个可能性。请注意，存在数字格式frac，但在这种情况下我无法使其工作。

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
% based on https://tex.stackexchange.com/a/34958/121799
\foreach \X [count=\Y] in {0,...,8}
{\pgfmathsetmacro{\myx}{\X*pi/4}
\ifnum\Y=1
\xdef\LstX{\myx}
\else
\xdef\LstX{\LstX,\myx}
\fi
}
\begin{tikzpicture}
\begin{axis}[domain=0:2*pi, ymax=1.2, samples=100, grid=major,
  xlabel=$\alpha$, ylabel=$\sin(\alpha)$, 
  xtick=\LstX,
      xticklabel={\pgfmathtruncatemacro{\tmp}{round(4*\tick/pi)}
      \pgfmathsetmacro{\mygcd}{gcd(\tmp,4)}%
      \pgfmathtruncatemacro{\mynumerator}{\tmp/\mygcd}%
      \pgfmathtruncatemacro{\mydenominator}{4/\mygcd}%
      \ifnum\mynumerator=0
       $\mathstrut\pgfmathprintnumber{0}$
      \else
       \ifnum\mynumerator=1
         \ifnum\mydenominator=1
          $\mathstrut\pi$       
         \else
          $\frac{\pi}{\pgfmathprintnumber{\mydenominator}}$     
         \fi
       \else
         \ifnum\mydenominator=1
          $\mathstrut\mynumerator\pi$       
         \else
          $\frac{\mynumerator\pi}{\pgfmathprintnumber{\mydenominator}}$
         \fi
       \fi
      \fi}, % https://tex.stackexchange.com/a/304032/121799
     ytick = {-1,-0.5,...,1}] %I assume this the part that I need to change?
    \addplot [blue](\x, {sin(deg(\x))});
\end{axis}
\end{tikzpicture}
\end{document}