迷你頁中四個數字下的兩個標題

Question

我有四個圖形，我希望在每組兩個圖形下方居中放置兩個標題，而不是在所有四個圖形下方放置一個標題（見下圖）。然而，如果我嘗試在前兩個小頁之後插入標題，所有圖形對齊都會變得混亂。如何正確地做到這一點？

\begin{figure}
    \centering
    % + +
    \begin{minipage}{.2\textwidth}
        \begin{tikzpicture}[transform canvas={scale=0.5}]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {0};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,0);
        \end{axis}
        \end{tikzpicture}
    \end{minipage}\hfill
    \begin{minipage}{.2\textwidth}
        \begin{tikzpicture}[transform canvas={scale=0.5}]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {x};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,1);
        \end{axis}
        \end{tikzpicture}
    \end{minipage}\hfill\quad\quad
    % + -
    \begin{minipage}{.2\textwidth}
        \begin{tikzpicture}[transform canvas={scale=0.5}]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {0};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        };
        \addplot [only marks, mark = -, color = blue] table {
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,0);
        \end{axis}
        \end{tikzpicture}
    \end{minipage}\hfill
    \begin{minipage}{.2\textwidth}
        \begin{tikzpicture}[transform canvas={scale=0.5}]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {-x};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        };
        \addplot [only marks, mark = -, color = blue] table {
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,-1);
        \end{axis}
        \end{tikzpicture}
    \end{minipage}
    \caption{Caption}
    \label{fig:my_label}

Answer 1

我想，你喜歡這樣的東西：

為了獲得這張圖片，我做了以下操作：

• 僅使用兩個迷你頁面，每個頁面用於一個表格環境
• 在表格環境中放置您的影像
• 稍微改變你的圖像——使它們更小並省略畫布轉換（這可能很棘手）
• 在每個小頁面中放置一個標題

完整的程式碼是：

\documentclass{article}

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

\usepackage[margin=30mm]{geometry}

\begin{document}
\begin{figure}[h]
\begin{minipage}{.48\textwidth}
    \begin{tabular}{cc}
        \begin{tikzpicture}[scale=0.45]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {0};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,0);
        \end{axis}
        \end{tikzpicture}

&         \begin{tikzpicture}[scale=0.45]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {x};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,1);
        \end{axis}
        \end{tikzpicture}

    \end{tabular}
\caption{Caption A}
\label{fig:my_label-A}
    \end{minipage}
\hfill
    \begin{minipage}{.48\textwidth}\centering
    \begin{tabular}{cc}
        \begin{tikzpicture}[scale=0.45]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {0};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        };
        \addplot [only marks, mark = -, color = blue] table {
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,0);
        \end{axis}
        \end{tikzpicture}
&
        \begin{tikzpicture}[scale=0.45]
        \begin{axis}[
                axis lines=middle,
                grid = major,
                xmin=-2, xmax=2,
                ymin=-2, ymax=2,
                xlabel=$x_1$,
                ylabel=$x_2$,
                xtick={-2,-1,0,...,2},
                ytick={-2,-1,0,...,2}]
        \addplot [thin, samples=100] {-x};
        \addplot [only marks, mark = +, color = red] table {
        -1 0
        };
        \addplot [only marks, mark = -, color = blue] table {
        0 1
        };
        \draw [-latex, red, thick] (0,0) -- (-1,-1);
        \end{axis}
        \end{tikzpicture}
    \end{tabular}
    \caption{Caption B}
    \label{fig:my_label}
    \end{minipage}
\end{figure}
\end{document}