3

I'd like to get the max/min value from a specific column table via function \findmax and \findmin in order to use it in ymin and ymax. I really dont get how \pgfplotstablesort function works. What would be perfect is to call \findmax{YAmax,YA,YAmin} and get back the maximum value of those 3 columns.

\documentclass{standalone}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\usepackage{filecontents}

\newcommand{\findmax}[1]{
    \pgfplotstablesort[sort key={#1},sort cmp={float >}]{\sorted}{data.dat}%
    \pgfplotstablegetelem{0}{1}\of{\sorted}%
    \let\ymax=\pgfplotsretval%
}

\begin{filecontents}{data.dat}
X   YA  YAmin   YAmax   YB  YBmin   YBmax
1   5   4   6   6   5   7
2   3   2   5   7   5   9
3   6   1   9   9   7   13
4   4   2   6   6   1   11
5   0   -1  3   3   0   5
6   1   -3  6   1   -1  2
\end{filecontents}



\begin{document}


\pgfplotsset{width=3cm,scale only axis}

\begin{tikzpicture}


%\findmax{YAmax,YA,YAmin}
%\findmin{YAmin,YA,YAmin}
\begin{axis}[at={(0,0)},title=YA]%,ymin=\ymin,ymax=\ymax]
\addplot [very thick,smooth,red,solid]  table [x=X, y=YA]   {data.dat}; 
\addplot [very thick,smooth,red,dotted]  table [x=X, y=YAmin]   {data.dat}; 
\addplot [very thick,smooth,red,dotted]  table [x=X, y=YAmax]   {data.dat}; 
\end{axis}

%\findmax{YBmax,YB,YBmin}
%\findmin{YBmax,YB,YBmin}
\begin{axis}[at={(4cm,0)},title=YB]%,ymin=\ymin,ymax=\ymax]
\addplot [very thick,smooth,red,solid]  table [x=X, y=YB]   {data.dat}; 
\addplot [very thick,smooth,red,dotted]  table [x=X, y=YBmin]   {data.dat}; 
\addplot [very thick,smooth,red,dotted]  table [x=X, y=YBmax]   {data.dat}; 
\end{axis}

\end{tikzpicture}
\end{document}
1

2 Answers 2

5

Finally done it.

Just created a function that finds the extrema of a chosen column of the external table.

\newcommand{\findmax}[1]{
  % Starting value for max : 0
  \pgfmathtruncatemacro{\mymax}{0}

  % Parsing each element of the first column
  \pgfplotsinvokeforeach {0,...,5}{
    \pgfplotstablegetelem{##1}{#1}\of{\mytable}
    \ifthenelse{ \pgfplotsretval >\mymax  }
    {\pgfmathtruncatemacro{\mymax}{\pgfplotsretval}} % valid
    {}  %invalid
  }
  \let\ymax=\mymax%
}
1
  • Could you provide a more coherent example of how to use the final solution? Commented Feb 22, 2021 at 21:40
1

With \pgfplotstablesort:

enter image description here

\begin{filecontents}[overwrite]{data.dat}
X   YA  YAmin   YAmax   YB  YBmin   YBmax
1   5   4   6   6   5   7
2   3   2   5   7   5   9
3   6   1   9   9   7   13
4   4   2   6   6   1   11
5   0   -1  3   3   0   5
6   1   -3  6   1   -1  2
\end{filecontents}


\documentclass[border=5mm, varwidth]{standalone}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
%  \pgfplotsset{width=3cm,scale only axis}
\usepackage{amsmath}

\begin{document}
\pgfplotstableread[]{data.dat}{\mytable}
\pgfplotstablegetrowsof{\mytable}
\pgfmathtruncatemacro\LastRowNo{\pgfplotsretval-1}
\pgfplotstabletypeset[]{\mytable}
%\pgfplotstablesort[sort key={YA}]{\sorted}{\mytable}
%\pgfplotstabletypeset[]{\sorted}

\newcommand{\findYmax}[1]{%
\pgfplotstablesort[sort key={#1}]{\sorted}{\mytable}%
    \pgfplotstablegetelem{\LastRowNo}{#1}\of{\sorted}%
\xdef\tempYmax{\pgfplotsretval}}

\newcommand{\findXmax}[1]{%
\pgfplotstablesort[sort key={#1}]{\sorted}{\mytable}%
    \pgfplotstablegetelem{\LastRowNo}{X}\of{\sorted}%
\xdef\tempXmax{\pgfplotsretval}}

\findXmax{YB}
\findYmax{YB}
$YB_{\max}=\tempYmax$  at $X_{\max}=\tempXmax.$

\begin{tikzpicture}
%\findmax{YAmax,YA,YAmin}
%\findmin{YAmin,YA,YAmin}
\begin{axis}[at={(0,0)},title=YA]%,ymin=\ymin,ymax=\ymax]
\addplot[very thick,smooth,red,solid]  table [x=X, y=YA]{data.dat} node[above]{YA}; 

\findXmax{YA}
\findYmax{YA}
\addplot[mark=*, blue]  coordinates{(\tempXmax,\tempYmax)} node[above]{$(X_{\max}, YA_{\max}) = (\tempXmax,\tempYmax) $}; 
\end{axis}
\end{tikzpicture}
\end{document}

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