pgfplots，以科学计数法获取轴指数

Question

很多时候，我都会使用和来制作堆叠时间历史图，xticks以xlabel节省论文中的垂直空间。

考虑以下 MWE：

\documentclass{standalone}
\usepackage{pgfplots}

\pgfplotsset{
  compat=1.14, 
  width=200pt,
  height=100pt,
}

\begin{document}

  \begin{tikzpicture}
    \begin{axis}[
      name = plot1,
      xticklabels={,,},
      ylabel = {$x_1$},
      xmajorgrids,
    ]
      \addplot coordinates {(1,0.0001)(2,0.0002)(3,0.0003)};
    \end{axis}

    \begin{axis}[
      at=(plot1.south west), anchor=north west,
      xlabel = {$t$[s]},
      ylabel = {$x_2$},
      xmajorgrids,
    ]
      \addplot coordinates {(1,0.0002)(2,0.0004)(3,0.0006)};
    \end{axis}

  \end{tikzpicture}%
\end{document}

其结果如下：

可以看出，y 轴乘数的位置有问题。一个可能的解决方案是在每个 y 刻度标签中用 指定乘数scaled y ticks=false，但结果会非常繁重且占用空间。

我希望能够务实地产生以下结果：

在我看来，它确实紧凑而优雅。

为了以编程方式执行此操作，需要科学计数法的指数，以便将其放入ylabel，例如：

ylabel = {$x_1 \cdot 10^{-\sci_exponent}$},

然后找到一种获取缩放的 ytick 标签的方法。

是否可以？

请注意，不同于自动将 PGFPlots xtick 刻度标签放入 x 轴标签中，我不想只移动指数，而是想反转指数以便（例如）代替$10^{4}，10^{-4}如上图所示。

Answer 1

致力于解决自动将 PGFPlots xtick 刻度标签放入 x 轴标签中，我想出了这个完全自动化的解决方案（即使有点肮脏）：

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.14}

\begin{document}

    \begin{tikzpicture}
    \begin{axis}[
        xtick scale label code/.code={\pgfmathparse{int(-#1)}$x \cdot 10^{\pgfmathresult}$},
        every x tick scale label/.style={at={(xticklabel cs:0.5)}, anchor = north},
        ytick scale label code/.code={\pgfmathparse{int(-#1)}$y \cdot 10^{\pgfmathresult}$},
        every y tick scale label/.style={at={(yticklabel cs:0.5)}, anchor = south, rotate = 90},
    ]

    \addplot coordinates { (0.0001,0.001)(0.0002,0.002)(0.0003,0.003) };

    \end{axis}
    \end{tikzpicture}

\end{document}

输出结果如下：

并自动适应数据的数量级。

Answer 2

作为Torbjørn T.已经在问题下面的评论中说明了不久前有一个类似的问题：自动将 PGFPlots xtick 刻度标签放入 x 轴标签中但我不喜欢那里提出的解决方案布多·津多维奇，因为这有几个副作用，我不想在这里提及。

因此我提出了另一种解决方案。有关其工作原理的更多详细信息，请查看代码中的注释。

（仅作为附加信息：
我已经询问过 Christian Feuersänger（PGFPlots 的作者），是否有可能只访问“比例值”，但到目前为止还没有得到答案。这将允许比这个更自动化的解决方案。如果有人已经有了想法，我会很高兴知道。）

\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
    % I think it is easier to use the `groupplots' library for your purpose
    % and in case you would have the "multipliers" in the *unit part* then
    % this would be very easy with the `units' library
    \usetikzlibrary{
        pgfplots.groupplots,
        pgfplots.units,
    }
    \pgfplotsset{
        % use this `compat' level or higher to use the improved positioning of axis labels
        compat=1.3,
        width=200pt,
        height=100pt,
        % state that we want to use the features of the `units' library
        use units=true,
        % what style do we want to use to show the units?
        unit markings=slash space,  % other options: parenthesis, square brackets
    }
% use the `siunitx' package to state (numbers and) units
\usepackage{siunitx}
\begin{document}
    \begin{tikzpicture}
            % to be consistent with the factoring, define the scaling factor here
            \def\Factor{4}
        \begin{groupplot}[
            group style={
                % we have 1 column with 2 rows of plots
                group size=1 by 2,
                % make the vertical sep a bit smaller than the default
                vertical sep=2ex,
                % we want to show the ticks and labels only at the plot at the bottom
                x descriptions at=edge bottom,
            },
            % set the xlabel and the corresponding unit; the later with the help of the
            % `siunitx' package
            xlabel= {$t$},
            x unit={\si{\second}},
            xmajorgrids,
            %%% change the scaling of the data
            % this is done automatically,
            % but to be consistent we provide it "manually" using the above defined variable
            scaled y ticks=base 10:\Factor,
            % but we don't want to show the label (here)
            ytick scale label code/.code={},
%            % both previous can be given manually with the following key
%            % (the both arguments correspond to the previous ones in reverse order)
%            scaled y ticks=manual:{}{\pgfmathparse{#1*1e\Factor}},
            %
            % to not have to add the "multiplier" to each `ylabel' apply it as
            % prefix to all
            execute at end axis={
                % (the `pgfplotsset' is necessary, because `execute at end axis'
                % only executes *executable* code and `ylabel/.add' is no executable code.)
                \pgfplotsset{
                    ylabel/.add={\num{e\Factor}\,}{},
                }
            },
        ]
        \nextgroupplot[
            % (as it seems this has to be done at every `\nextgroupplot' manually:)
            % add the "multiplier" to each `ylabel'
            % of course also here we use the defined factor to be consistent between the
            % "automatic" scaling and the factor in the label
            ylabel={$x_1$},
        ]
            \addplot coordinates { (1,0.0001)(2,0.0002)(3,0.0003) };
        \nextgroupplot[
            ylabel={$x_2$},
        ]
            \addplot coordinates { (1,0.0002)(2,0.0004)(3,0.0006) };
        \end{groupplot}
    \end{tikzpicture}
\end{document}