从外部 .dat 文件设置轴限制（xmin、xmax、ymin、ymax）

Question

我正在从 matlab 生成的 .dat 文件中导入绘图数据。我还想从文件中设置轴限值.dat。有没有办法从矩阵中的表格中设置 xmin、xmax、ymin 和 ymax .dat（如稍后绘制的数据）？我目前设置轴限值的方式如下所示。

\documentclass{standalone}
\usepackage{tikz} 
\usepackage{pgfplots}
\usepackage{pgf,pgffor}
\pgfplotsset{compat=1.15}

\def\names{{Folder1/}{Folder2/}{Folder3/}}

\foreach \x in \names{
\graphicspath{ \x {Icons/}}  

\begin{document}

    \begin{tikzpicture} 

    \begin{axis}[
    enlargelimits = false,
    hide axis,
    ]
        \addplot graphics [
            xmin=-80.5430, xmax=-80.5150,
            ymin=43.4580, ymax=43.4740,
            ]{ov2.png};
        \addplot[
            only marks,
            mark=text,
            text mark={\includegraphics[scale=0.02]{icon.png}}
        ]
        table [search path={\x}]{overnight.dat};
        \end{axis}
    \end{tikzpicture}

\end{document}

我希望在包含轴限值的文件中定义 xmin xmax，而不是在代码中定义它们（它们不是正在绘制的数据的函数，而是正在叠加的.dat图像角落的 GPS 坐标）ov2.png

Answer 1

如前所述，您可以使用\pgfplotstablegetelem来访问数据文件的单个元素。这需要您知道它的行和列。值以 返回\pgfplotsretval。列可以通过名称引用，行可以通过其索引引用，从 0 开始。

还可以使用 循环遍历列并对每个值执行某些操作\pgfplotstableforeachcolumnelement。例如，这可用于查找最小值、最大值或平均值。

为此编写几个宏是个好主意，尤其是在第二种情况下。以下代码显示了一些示例：

\documentclass[border=2mm]{standalone}
\usepackage{pgfplots}
\usepackage{filecontents}

\begin{filecontents}{data.csv}
x y
-1.5 27.3
-1.0 24.8
-0.5 22.1
0.0 30.7
0.5 11.3
1.0 15.9
1.5 20.4
2.0 21.8
2.5 22.8
\end{filecontents}

% read the table
\pgfplotstableread{data.csv}\datatable

% get specific element and store it in a macro
% #1: table
% #2: row
% #3: column (name or [index]<index>)
% #4: macro for value
\newcommand*{\GetElement}[4]{%
    \pgfplotstablegetelem{#2}{#3}\of{#1}%
    \let#4\pgfplotsretval
}

% get the first element of a column and store it in a macro
% #1: table
% #2: column (name or [index]<index>)
% #3: macro for value
\newcommand*{\GetFirstElement}[3]{%
    \GetElement{#1}{0}{#2}{#3}%
}

% get the last element of a column and store it in a macro
% #1: table
% #2: column (name or [index]<index>)
% #3: macro for value
\newcommand*{\GetLastElement}[3]{%
    \pgfplotstablegetrowsof{#1}%
    \pgfmathsetmacro\lastrowidx{int(\pgfplotsretval - 1)}%
    \GetElement{#1}{\lastrowidx}{#2}{#3}%
}

% get maximum and minimum value of a column and store them in macros
% #1: table
% #2: column
% #3: macro for max
% #4: macro for min
\newcommand*{\GetMinMax}[4]{%
    \pgfmathsetmacro#3{-16383}%
    \pgfmathsetmacro#4{16383}%
    \pgfplotstableforeachcolumnelement{#2}\of{#1}\as\cellValue{%
        \ifx\cellValue\@empty\else
            \pgfmathsetmacro{#3}{max(#3,\cellValue)}%
            \pgfmathsetmacro{#4}{min(#4,\cellValue)}%
        \fi
    }
}

% get average of column and store it in a macro
% #1: table
% #2: column
% #3: macro for average
\newcommand*{\GetAverage}[3]{%
    \pgfplotstablegetrowsof{#1}%
    \let\rownumber\pgfplotsretval
    \def#3{0}%
    \pgfplotstableforeachcolumnelement{#2}\of{#1}\as\cellValue{%
        \ifx\cellValue\@empty
            % don't count emplty cells
            \pgfmathsetmacro{\rownumber}{\rownumber - 1}%
        \else
            \pgfmathsetmacro{#3}{#3 + \cellValue}%
        \fi
    }
    \pgfmathsetmacro{#3}{#3 / \rownumber}%
}


\GetMinMax{\datatable}{x}{\dataxmax}{\dataxmin}
\GetMinMax{\datatable}{y}{\dataymax}{\dataymin}
\GetElement{\datatable}{5}{y}{\value}
\GetFirstElement{\datatable}{y}{\first}
\GetLastElement{\datatable}{y}{\last}
\GetMinMax{\datatable}{x}{\dataxmax}{\dataxmin}
\GetMinMax{\datatable}{y}{\dataymax}{\dataymin}
\GetAverage{\datatable}{y}{\average}

\begin{document}
\begin{tikzpicture}
\begin{axis}[%
    xlabel=$x$-label,
    ylabel=$y$-label,
    xmin=\dataxmin, xmax=\dataxmax,
    ymin=\dataymin, ymax=\dataymax,
]
\addplot table[x=x,y=y] {\datatable};
\draw[red] (axis cs:\dataxmin,\value) -- node[pos=0.35, above] {\value} (axis cs:\dataxmax,\value);
\draw[green] (axis cs:\dataxmin,\first) -- node[pos=0.07, above] {\first} node[pos=0.93, above] {\last} (axis cs:\dataxmax,\last);
\draw[cyan] (axis cs:\dataxmin,\average) -- node[pos=0.25, below] {average $=$ \average} (axis cs:\dataxmax,\average);
\end{axis}
\end{tikzpicture}
\end{document}