将刻度放置在间隔标签附近

Question

我必须制作一个在间隔标签处有刻度的图（不在标签之间的线段中间）。下图中预期的变化用红色标记。顺便问一句：是否存在一种自动写入刻度的方法（不是通过明确写入每个点xtick={1838,1843,etc.}）？MWE：

\documentclass{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
    xmin=1838,
    xmax=1862,
    x tick label as interval,
    xticklabel={
        \pgfmathprintnumber\tick\discretionary{--}{--}{--}\pgfmathparse{\nexttick-1}\pgfmathprintnumber\pgfmathresult
    },
    xtick={1838,1843,1848,1853,1858,1863},
    xticklabel style={
        align=center,
        text width=1cm,
        execute at begin node=\setlength{\baselineskip}{8pt},
        rotate=90,
        anchor=east
    },
    xmajorgrids,
]
\addplot
  table[row sep=crcr]{%
1840    8\\
1845    7\\
1850    6\\
1855    4\\
1860    4\\
};
\end{axis}
\end{tikzpicture}
\end{document}

Answer 1

这是一个使用该pgfplotstable包的功能的解决方案。

这样就可以计算表中两个条目之间的偏移量，假设这些条目间距均匀。然后使用偏移量来虚拟计算和排版，而\nexttick无需调用x ticklabels as interval。xtick还定义了以xtick=data避免手动输入。

有两点我不太确定：

• 价值观xticklabels
• y 轴上的红色十字

    \documentclass{standalone}
    \usepackage{pgfplots}
    \usepackage{pgfplotstable}

    \begin{document}
    % Get number of rows
    \pgfplotstableread[row sep=crcr]{
        1840    8\\
        1845    7\\
        1850    6\\
        1855    4\\
        1860    4\\
    }\loadedtable

    % Row amount of the source table
    \pgfplotstablegetrowsof{\loadedtable}
    \pgfmathtruncatemacro{\numrows}{\pgfplotsretval}
    % Number of last row (numbering starts at 0)
    \pgfmathtruncatemacro{\lastrow}{\numrows-1}
    % First value in data
    \pgfplotstablegetelem{0}{[index]0}\of{\loadedtable}
    \pgfmathsetmacro{\databegin}{\pgfplotsretval}
    % Last value in data
    \pgfplotstablegetelem{\lastrow}{[index]0}\of{\loadedtable}
    \pgfmathsetmacro{\dataend}{\pgfplotsretval}
    % Data step (assumes uniform step)
    \pgfmathsetmacro{\datashift}{(\dataend-\databegin)/(\numrows-1)}

    \begin{tikzpicture}
        \begin{axis}[
                xticklabel={\pgfmathprintnumber{\tick}\discretionary{--}{--}{--}\pgfmathparse{\tick+\datashift-1}\pgfmathprintnumber\pgfmathresult},
                xtick=data,
                xticklabel style={
                    align=center,
                    text width=1cm,
                    execute at begin node=\setlength{\baselineskip}{8pt},
                    rotate=90,
                    anchor=east,
                    %yshift={\xticklabelyshiftcoeff*\pgfkeysvalueof{/pgfplots/width}}
                    },
                y tick label as interval,
                xmajorgrids,
                enlarge x limits=false,
                clip marker paths=false,
            ]
            \addplot table {\loadedtable};
        \end{axis}
    \end{tikzpicture}
    \end{document}