Pgfplots：仅针对每个第二个 x 轴的网格

Question

我只想为每个第二个 x 数据点设置网格。例如：我想要一条网格线，一个点 c 和 d，但不在两者之间。我希望我描述清楚了。这可能吗？我在文档中没有找到任何东西。

\documentclass[12pt]{article}
\usepackage{pgfplots}

\begin{document}
\begin{figure}
\begin{tikzpicture}
\begin{axis}[
    width=15cm,
    height=8cm,
    xmin=0, xmax=9,
    ymin=0, ymax=10,
    ytick={0, 5},
    yticklabels={0, x},
    xtick={0, 0,5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9},
    xticklabels={,a,, b,, c,, d,, e,, f,, g,, h,, i}, 
    xmajorgrids={true},
    x tick label style={rotate=45},
    y label style={at={(axis description cs:0, 0.5)},anchor=south},
    ylabel={estimation}     
    ]
    \legend{test1 a, test2 b}       
    \addplot coordinates {
        (0, 0)
        (1, 2)
        (2, 2.2)
        (3, 6)
        (4, 6)
        (5, 7.5)
        (6, 7.5)
        (7, 0)
        (8, 4)
        (9, 0)
    };

    \addplot [red] coordinates {(0, 5) (9, 5)};
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}

Answer 1

像这样？

\usepackage{pgfplots}

\begin{document}
\begin{figure}
\begin{tikzpicture}
\begin{axis}[
    width=15cm,
    height=8cm,
    xmin=0, xmax=9,
    ymin=0, ymax=10,
    ytick={0, 5},
    yticklabels={0, x},
    xtick={0, ..., 9},
    xticklabels={,a, b, c, d, e, f, g, h, i}, 
    xmajorgrids={true},
    minor x tick num=1,
    x tick label style={rotate=45},
    y label style={at={(axis description cs:0, 0.5)},anchor=south},
    ylabel={estimation}     
    ]
    \legend{test1 a, test2 b}       
    \addplot coordinates {
        (0, 0)
        (1, 2)
        (2, 2.2)
        (3, 6)
        (4, 6)
        (5, 7.5)
        (6, 7.5)
        (7, 0)
        (8, 4)
        (9, 0)
    };

    \addplot [red] coordinates {(0, 5) (9, 5)};
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}