PGFPlots：为一个点定制注释

Question

我有以下散点图：

\documentclass[class=elsarticle]{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
enlargelimits=0.2,
xlabel=Depth, ylabel=Breadth
]
\addplot+[nodes near coords,only marks,
point meta=explicit symbolic]
table[meta=label] {
Depth Breadth label
2.57 3.59 Cambridge
2.58 4.27 Dresden
2.45 3.77 {Palo\ Alto}
2.61 2.10 Asan
2.03 4.17 Heidelberg
2.25 4.29 Yamagata
};
\end{axis}
\end{tikzpicture}
\end{document}

我怎样才能将cambridge标签放置在标记下方？

Answer 1

您可以这样做，尽管目前还不够简单。（在PGFPlots 追踪器为了那个原因。）

有关更多详细信息，请查看代码中的注释。

% used PGFPlots v1.14
    % to provide the table only once either put it in an external file or
    % load it to a command
    % (because there currently is a bug in PGFPlotsTable when using filtering
    %  in a "loaded" table
    %      <https://sourceforge.net/p/pgfplots/bugs/109/>
    %  we have to store the data in a file)
    \begin{filecontents*}{mydata.txt}
        Depth   Breadth label
        2.57    3.59    Cambridge
        2.58    4.27    Dresden
        2.45    3.77    {Palo Alto}
        2.61    2.10    Asan
        2.03    4.17    Heidelberg
        2.25    4.29    Yamagata
    \end{filecontents*}
\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
    \pgfplotsset{
        % use this `compat' level or higher to make use of the improved
        % positioning of the axes labels
        compat=1.3,
        % create styles to filter stuff and apply different `nodes near coords' styles
        % (borrowed from <http://tex.stackexchange.com/a/301991/95441>)
        discard if/.style 2 args={
            % suppress LOG messages about the filtered points
            filter discard warning=false,
            x filter/.append code={
                \edef\tempa{\thisrow{#1}}
                \edef\tempb{#2}
                \ifx\tempa\tempb
                    \def\pgfmathresult{NaN}
                \fi
            },
        },
        % here we want an OR combination so we have to modify the code a bit
        % (`.append style' --> `.style')
        discard if not/.style 2 args={
            % suppress LOG messages about the filtered points
            filter discard warning=false,
            x filter/.code={
                \edef\tempa{\thisrow{#1}}
                \edef\tempb{#2}
                \ifx\tempa\tempb
                \else
                    \def\pgfmathresult{NaN}
                \fi
            },
        },
        % define the style of the `nodes near coords' that should be shown
        % above the point
        nodes near coords above style/.style={
            nodes near coords style={
                anchor=south,
            },
        },
        % define the style of the `nodes near coords' that should be shown
        % below the point
        nodes near coords below style/.style={
            nodes near coords style={
                anchor=north,
            },
        },
    }
\begin{document}
    \begin{tikzpicture}
        \begin{axis}[
            enlargelimits=0.2,
            xlabel=Depth,
            ylabel=Breadth,
            only marks,
            nodes near coords,
            point meta=explicit symbolic,
            table/meta=label,
        ]
            % first draw all points that should show the `nodes near coords'
            % above the points
            \addplot+ [
                % if *all* points -- also the ones with the other style(s) --
                % should show the same style (except the `nodes near coords')
                % then add `forget plot', so the `cycle list' index isn't
                % increased
                forget plot,
                % apply the style which should be used
                nodes near coords above style,
                % state all the elements that should be filtered away
                discard if={label}{Cambridge},
                discard if={label}{Heidelberg},
            % unfortunately there seems to be a bug that the filtering
            % doesn't work for "stored" tables ...
%            ] table {\datatable};
            % ... that is, why we have to use the values stored in an external file
            ] table {mydata.txt};

            % to apply the other style we need to loop through the elements
            % which should get the other style
            % (so the list should consist of the same names as above)
            % the rest should be pretty clear now how it works
            \pgfplotsinvokeforeach {
                Cambridge,
                Heidelberg%
            } {
                \addplot+ [
                    forget plot,
                    nodes near coords below style,
                    discard if not={label}{#1},
                ] table {mydata.txt};
            }
        \end{axis}
    \end{tikzpicture}
\end{document}