5

I have

succeeded plotting list data, generated from Matlab, as a contour in tikz-pgf using gnuplot. The data is arranged as

1,-6.2832,-6.2832,0.74038
2,-6.2832,-6.1563,0.74997
3,-6.2832,-6.0293,0.75982
4,-6.2832,-5.9024,0.76986
.......

The addplot works with

\addplot3[mesh/rows=100,mesh/num points=10000,contour gnuplot={
                    number=24,
                    % cdata should not be affected by z filter:
                    output point meta=rawz,
                    labels=false,
                }] table [x index={1}, y index={2}, z index={3}] {\datatable};

resulting contour[1]]

The question:

I want to do the same using matrix data, as that seems to run much faster. How do I do that, how do I have to format the data? Here the not quite minimal MWE:

\documentclass{report}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\usepackage[dvipsnames]{xcolor}

\usepackage{tikz,pgfplots,pgfplotstable,pgffor,pgfmath,tikz-3dplot}

%===================================================
\usetikzlibrary{positioning,plotmarks,pgfplots.colormaps,external,3d,calc,arrows}
\usetikzlibrary{decorations,decorations.pathmorphing,decorations.pathreplacing}
\usetikzlibrary{shapes,arrows}
\tikzexternalize[mode=convert with system call,shell escape=-enable-write18]
%===================================================

%==== Tikz & PGF Camera alignment macro ============
% Style to set TikZ camera angle, like PGFPlots `view`
\tikzset{viewport/.style 2 args={
    x={({cos(-#1)*1cm},{sin(-#1)*sin(#2)*1cm})},
    y={({-sin(-#1)*1cm},{cos(-#1)*sin(#2)*1cm})},
    z={(0,{cos(#2)*1cm})}
}}
%===================================================

%Define standard arrow tip
\tikzset{>=stealth',}

% Color Map
\pgfplotsset{
    colormap={colormap2}{
        color(0cm)=(blue!70!black);
        color(1cm)=(cyan!60!black)
    }
}

%==== Externalisation ==============================
\makeatletter
\newcommand{\useexternalfile}[2][Tikz] % \useexternalfile[Folder]{Filename}
{
    \tikzsetnextfilename{#2-output}
    \input{#1/#2.tikz}
}
\makeatother
%===================================================

\begin{document}

\begin{tikzpicture}

    \pgfplotstableread[col sep = comma]{Matrix.csv}\datatable

    \begin{axis}
    [
        view={0}{90},
        scale only axis,
        colormap name={colormap2},
        ticks=none
    ]
        \addplot3[surf, mesh/rows=100, mesh/cols=100] table {\datatable};

    \end{axis}

\end{tikzpicture}

\end{document}

Using this, I get the error

Package pgfplots Error: the arguments of [mesh/rows=100,mesh/cols=100] assume 10000 points, but I got actually N = 100 points!
The data matrix appears to be incomplete or overcomplete!?

where my Matrix.csv is of the form

0.74038,0.74228,0.744,0.74549,0.74672,......,0.27529
0.74997,0.75246,0.75477,0.75685,0.75867,.....,0.26786
.....

i.e. every line has 100 points of data and there are 100 lines. Data in one line is separated by comma and lines are separated by newline.

3

Your original input is the only and correct supported way how to communicate matrix data to pgfplots, i.e. by providing one matrix cell per row.

A format which provides the Z data as matrix in which each line in the input file is one row of the entire matrix is currently unsupported.

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