pgfplots：在 ybar 图中标记比绘图区域更高的条形图

Question

我想以某种方式指示高于绘图区域的条形的值。也许通过将标签放在条形内或绘图区域边界上方。请注意，我只想要“离开”绘图区域的条形的标签，也就是说，(b, 7)在(c, 6)这种情况下。
我想要：

我有：

我正在尝试nodes near cords和point meta=explicit symbolic选项，但目前还没有成功。

\begin{tikzpicture}
\begin{axis}[
  ybar,
  symbolic x coords={a, b, c},
  xtick=data,
  ymax=5,
  % nodes near coords,
  % nodes near coords align={vertical},
  % point meta=explicit symbolic
]

\addplot coordinates {(a, 3)  (b, 7)[7]   (c, 1)    };
\addplot coordinates {(a, 2)  (b, 4)      (c, 6)[6] };
\addplot coordinates {(a, 4)  (b, 1)      (c, 3)    };

\end{axis}
\end{tikzpicture}

Answer 1

这可以通过修改来实现这个答案。有关其工作原理的详细信息，请查看代码中的注释。

% used PGFPlots v1.14
\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
        % create a variable to store the `ymax' value
        \pgfmathsetmacro{\ymax}{5}
    \begin{axis}[
        ybar,
        symbolic x coords={a, b, c},
        xtick=data,
        % use the previously created variable here
        ymax=\ymax,
        % (this i just added so the outer most bars aren't clipped partially)
        enlarge x limits={0.2},
        % -----------------------------------------------------------------
        % we store the *original* y value in a variable ...
        visualization depends on={rawy \as \rawy},
        % ... which value should be shown in the `nodes near coords' ...
        nodes near coords={\pgfmathprintnumber\rawy},
        % ... and we want to limit the range of the bars to the axis limits
        restrict y to domain*={
            \pgfkeysvalueof{/pgfplots/ymin}:\pgfkeysvalueof{/pgfplots/ymax}
        },
        % ---------------------------------------------------------------------
        % now we create a style for the `nodes near coords' which is dependend
        % on the value
        % (adapted from <http://tex.stackexchange.com/a/141006/95441>)
        % (#1: the THRESHOLD after which we switch to a special display)
        nodes near coords greater equal only/.style={
            % define the style of the nodes with "small" values
            small value/.style={
                /tikz/coordinate,
            },
            every node near coord/.append style={
                check for small values/.code={
                    \begingroup
                    % this group is merely to switch to FPU locally.
                    % Might be unnecessary, but who knows.
                    \pgfkeys{/pgf/fpu}
                    \pgfmathparse{\pgfplotspointmeta<#1}
                    \global\let\result=\pgfmathresult
                    \endgroup
                    %
                    % simplifies debugging:
                    %\show\result
                    %
                    \pgfmathfloatcreate{1}{1.0}{0}
                    \let\ONE=\pgfmathresult
                    \ifx\result\ONE
                        % AH: our condition 'y < #1' is met.
                        \pgfkeysalso{/pgfplots/small value}
                    \fi
                },
                check for small values,
            },
        },
        % asign a value to the new style which is the threshold at which
        % the `small value' style is used.
        % Of course in this case it should be the `\ymax' value
        nodes near coords greater equal only=\ymax,
        % -----------------------------------------------------------------
    ]
        \addplot coordinates {(a, 3) (b, 7) (c, 1)};
        \addplot coordinates {(a, 2) (b, 4) (c, 6)};
        \addplot coordinates {(a, 4) (b, 1) (c, 3)};
    \end{axis}
\end{tikzpicture}
\end{document}