表格中的散点图，其中标记由元列值设置

Question

我的输入数据是一个包含多列和多行的 txt 文件。最后一列的值始终是一个整数，取值为 0、1、2 或 3。

我需要一个散点图，它根据最终值具有不同的标记。

\documentclass{article}
\usepackage{pgfplots}
\usepackage{filecontents}
\begin{filecontents*}{data.txt}
12.3458,0.709423,0.018174,10.3177,0.031258,0.360285,0.071809,0
13.3458,0.709423,0.018174,10.3177,0.031258,0.360285,0.171809,0
7.88918,0.037782,0.010597,13.0123,0.027078,0.345659,0.070872,1
8.88918,0.037782,0.010597,13.0123,0.027078,0.345659,0.170872,1
3.29679,0.175776,0.012142,18.2475,0.031448,0.292123,0.141521,2
4.29679,0.175776,0.012142,18.2475,0.031448,0.292123,0.241521,2
3.94161,0.204657,0.002334,2.09774,0.011567,0.278266,0.113811,3
4.94161,0.204657,0.002334,2.09774,0.011567,0.278266,0.213811,3
\end{filecontents*}

\begin{document}

\begin{tikzpicture}
    \pgfplotstableread[col sep=comma] {data.txt}\thedata
    \begin{axis}[width=7cm,height=7cm]
        \addplot[scatter,
                 only marks,
%                visualization depends on={value \thisrow{index 7} \as \labela},
%                scatter/@pre marker code/.append style = {/tikz/mark=\labela},
                 ] table[x index=0,y index=6] {\thedata};
    \end{axis}
\end{tikzpicture}

\end{document}

导致

当我取消注释这些行时，没有出现任何标记。

• 我需要定义要使用的标记：例如， x, o, sqaure, triangle只有 4 个。
• 最好，我需要设置它们的颜色（例如x是红色，o是蓝色，square是绿色，triangle是黑色）
• 该图表将在具有不同数据的文档中多次使用。
• 如果可能的话，我希望保持pgfplotstableread在范围内tikzpicture。

pgfplots 手册的第 187 页看起来相关，但我无法进一步了解

还有一些其他帖子非常有帮助，但它们都没有将整数转换为标记符号：

在 PGFPlots 中，使用元数据作为标记？

PGFPlots 中不同颜色的元数据

如何使用 pgfplots 绘制散点，颜色由表 rgb 值定义？

Answer 1

你可以按如下方式使用它：不要使用以 开头的宏名\the。这是 TeX 的特殊情况，可能会导致很难调试的错误。

\documentclass{article}
\usepackage{pgfplotstable}

\begin{document}
\begin{tikzpicture}
\pgfplotstableread[col sep=comma,header=false]{
12.3458,0.709423,0.018174,10.3177,0.031258,0.360285,0.071809,0
13.3458,0.709423,0.018174,10.3177,0.031258,0.360285,0.171809,0
7.88918,0.037782,0.010597,13.0123,0.027078,0.345659,0.070872,1
8.88918,0.037782,0.010597,13.0123,0.027078,0.345659,0.170872,1
3.29679,0.175776,0.012142,18.2475,0.031448,0.292123,0.141521,2
4.29679,0.175776,0.012142,18.2475,0.031448,0.292123,0.241521,2
3.94161,0.204657,0.002334,2.09774,0.011567,0.278266,0.113811,3
4.94161,0.204657,0.002334,2.09774,0.011567,0.278266,0.213811,3
}\mydata

\begin{axis}[width=7cm,height=7cm]
\addplot+[scatter, only marks,
  scatter/classes={0={mark=square*,green},
                   1={mark=triangle*,black},
                   2={mark=o,blue},
                   3={mark=x,red}
                  },
  scatter src=explicit symbolic
  ] table[x index=0,y index=6,meta index=7] \mydata;
\end{axis}

\end{tikzpicture}

\end{document}