[Tex/LaTex] Conditional color and mark style for scatter plot in PGFPlots

groupplotspgfplotspgfplotstabletikz-pgf

I have a data file that has two columns each containing a class, one for color (QoI) and one for marker type (type). I would like points that have have the same QoI value be the same color, but have a different marker type for each type. There are only two different value for type, but several for QoI. I can get the colors working, but cannot figure out how to incorporate different marker styles. I couldn't find a way to use multiple values of meta, but perhaps there's another solution.

There are multiple plots that will be reading from multiple files, though for the MWE below they all read the same data. I just want to make sure the solution also works with groupplots.

MWE

\documentclass[]{standalone}
\usepackage{tikz, pgf, pgfplots, pgfplotstable}
\usepgfplotslibrary{groupplots} % LATEX and plain TEX
\pgfplotsset{compat=1.15}
\usepgfplotslibrary{colorbrewer}
\pgfplotsset{cycle list/Dark2}
\usepackage{filecontents}
\begin{filecontents}{data.dat}
  QoI model surrogate type outname QoI_group error_scaled
  1 -1 -1.01224658575 training Q1 1 0.014956929466
  1 -0.977952092966 -0.984618496392 training Q1 1 0.014956929466
  2 0.53568190987 0.521776331357 training Q2 1 0.0158105026132
  3 0.798208448928 0.789090773894 training Q3 1 0.044540998773
  4 0.378407928561 0.326243792219 training Q4 1 0.0274695358287
  4 0.355049936935 0.33464474407 training Q4 1 0.0274695358287
  3 0.762183505103 0.681415197111 validation Q3 1 0.044540998773
  3 0.822636091166 1.02086372811 validation Q3 1 0.044540998773
\end{filecontents}

\begin{document}
\begin{tikzpicture}[font=\small]
  \tikzset{mark options={mark size=2, opacity=0.5}}
  \begin{groupplot}[group style={group size=3 by 1, horizontal sep=1em},
    width=7cm, height=7cm,
    ymin=-1.2, ymax=1.2, xmin=-1.2, xmax=1.2,
    scatter/classes={1={Dark2-A}, 2={Dark2-B}, 3={Dark2-C}, 4={Dark2-D}},
    scatter,
    scatter src=explicit symbolic,
    ]
    \nextgroupplot[title={1}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={2}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={3}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};    
  \end{groupplot}
\end{tikzpicture}
\end{document}

Response to answer addendum

I added some comments to the code below to make more clear what I am trying to achieve. I think I was mistaken, I thought you could "cycle" through colors /based on/ the values of QoI. If that is not the case, do I have to explicitly define the scatter/classes? I could not find an example in the manual, so perhaps that is what is needed.

\documentclass[]{standalone}
\usepackage{tikz, pgf, pgfplots, pgfplotstable}
\usepgfplotslibrary{groupplots} % LATEX and plain TEX
\pgfplotsset{compat=1.15}
\usepgfplotslibrary{colorbrewer}
\usetikzlibrary{plotmarks}
\pgfplotsset{cycle list/Dark2}

\pgfdeclareplotmark{training}{
  \pgfpathcircle{\pgfpoint{0pt}{0pt}}{2pt}\pgfusepathqfillstroke}
\pgfdeclareplotmark{validation}{
  \pgfpathmoveto{\pgfpoint{-2pt}{-1pt}}
  \pgfpathlineto{\pgfpoint{2pt}{-1pt}}
  \pgfpathlineto{\pgfpoint{0pt}{2pt}}
  \pgfpathlineto{\pgfpoint{-2pt}{-1pt}}
  \pgfusepathqfillstroke}
\usepackage{filecontents}
\begin{filecontents}{data.dat}
  QoI model surrogate type outname QoI_group error_scaled
  1 -1 -1.01224658575 training Q1 1 0.014956929466                      % Color 1, mark style 1 (until "type"="validation")
  1 -0.977952092966 -0.984618496392 training Q1 1 0.014956929466        % Color 1
  2 0.53568190987 0.521776331357 training Q2 1 0.0158105026132          % Color 2
  3 0.798208448928 0.789090773894 training Q3 1 0.044540998773          % Color 3
  4 0.378407928561 0.326243792219 training Q4 1 0.0274695358287         % Color 4
  4 0.355049936935 0.33464474407 training Q4 1 0.0274695358287          % Color 4
  3 0.762183505103 0.681415197111 validation Q3 1 0.044540998773        % Color 3, mark style 2
  3 0.822636091166 1.02086372811 validation Q3 1 0.044540998773         % Color 3, mark style 2
\end{filecontents}

\begin{document}
\begin{tikzpicture}[font=\small]
  \tikzset{mark options={mark size=2, opacity=0.5}}
  \begin{groupplot}[group style={group size=3 by 1, horizontal sep=1em},
    width=7cm, height=7cm,
    ymin=-1.2, ymax=1.2, xmin=-1.2, xmax=1.2,
    % Commenting out scatter/classes removes meta color coding.
    % Is there a way that I can automatically cycle the colors in scatter/classes
    % so I don't have to define each explicitly, and so they'll reset for each \addplot+?
    scatter/classes={1={Dark2-A}, 2={Dark2-B}, 3={Dark2-C}, 4={Dark2-D}},
    scatter,
    scatter src=explicit symbolic,
    visualization depends on={value \thisrow{type}  \as \Type},
    visualization depends on={value \thisrow{QoI}  \as \QoI},
    scatter/@pre marker code/.append style={/tikz/mark=\Type},
    % point meta=\coordindex     % This wasn't needed.
    ]
    \nextgroupplot[title={1}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={2}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={3}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};    
  \end{groupplot}
\end{tikzpicture}
\end{document}

Best Answer

An answer inspired by this answer and this answer. You only need to name your symbols somehow and use them like in the example of page 402 of the pgfplots manual. That is, you can use visualization depends on and then change the symbols with scatter/@pre marker code. UPDATE: I dropped the definition of the symbols, which I did for fun (and I stressed that). I do not think that discarding some part of the data and using \addplot over and over is very elegant.

\documentclass[]{standalone}
\usepackage{tikz, pgf, pgfplots, pgfplotstable}
\usepgfplotslibrary{groupplots} % LATEX and plain TEX
\pgfplotsset{compat=1.15}
\usepgfplotslibrary{colorbrewer}
\usetikzlibrary{plotmarks}
\pgfplotsset{colormap/Dark2,
cycle list/Dark2,
    }

\pgfdeclareplotmark{training}{\pgfuseplotmark{*}}
\pgfdeclareplotmark{validation}{\pgfuseplotmark{square}}

\usepackage{filecontents}
\begin{filecontents}{data.dat}
  QoI model surrogate type outname QoI_group error_scaled
  1 -1 -1.01224658575 training Q1 1 0.014956929466                      % Color 1, mark style 1 (until "type"="validation")
  1 -0.977952092966 -0.984618496392 training Q1 1 0.014956929466        % Color 1
  2 0.53568190987 0.521776331357 training Q2 1 0.0158105026132          % Color 2
  3 0.798208448928 0.789090773894 training Q3 1 0.044540998773          % Color 3
  4 0.378407928561 0.326243792219 training Q4 1 0.0274695358287         % Color 4
  4 0.355049936935 0.33464474407 training Q4 1 0.0274695358287          % Color 4
  3 0.762183505103 0.681415197111 validation Q3 1 0.044540998773        % Color 3, mark style 2
  3 0.822636091166 1.02086372811 validation Q3 1 0.044540998773         % Color 3, mark style 2
\end{filecontents}

\begin{document}
\begin{tikzpicture}[font=\small]
  \tikzset{mark options={mark size=2, opacity=0.5}}
  \begin{groupplot}[group style={group size=3 by 1, horizontal sep=1em},
    width=7cm, height=7cm,
    ymin=-1.2, ymax=1.2, xmin=-1.2, xmax=1.2,
    scatter,
    visualization depends on={value \thisrow{type}  \as \Type},
    visualization depends on={value \thisrow{QoI}  \as \QoI},
    scatter/@pre marker code/.append style={/tikz/mark=\Type},
    point meta=explicit
    ]
    \nextgroupplot[title={1}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={2}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};
    \nextgroupplot[title={3}, yticklabels={,,}]
    \addplot[only marks] table[x=model, y=surrogate, meta=QoI] {data.dat};    
  \end{groupplot}
\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] How to automatically mark local extrema with pgfplots and scatter

There are some numerical inaccuracies involved here: The range of \pgfplotspointmetatransformed should be from 0 to 1000, where 0 is the point with the lowest meta value (by default, the meta value is the same as the y coordinate), and 1000 is the maximum value. However, it seems that the maximum value is sometimes something along the lines of 999.9876 or 1000.0422.

I took another look at the code, and found that there's actually a better way to determine the extreme values: They're already stored in the macros \pgfplots@metamin and \pgfplots@metamax. So we can simply use \ifx\pgfplots@metamax\pgfplotspointmeta to check whether we have the maximum value.

To be able to use the maximum to draw a vertical line, we can place a \coordinate node. This can only be accessed after the axis is finished, so you'll need to put your drawing command into the after end axis/.code={...} option. Setting

after end axis/.code={
        \draw [thick, dashed, gray] (maximum) --({axis cs:0,0}-|maximum);
}

will draw a vertical line from the maximum to the 0 line. For boxed plots, you should use rel axis cs:0,0 instead of axis cs:0,0, so the line goes all the way to the edge of the plot area.

\documentclass[preview=false,tikz=true]{standalone}
\usepackage{pgfplots}
\makeatletter
\pgfplotsset{
    /tikz/max node/.style={
        anchor=south,
    },
    /tikz/min node/.style={
        anchor=north,
        name=minimum
    },
    mark min/.style={
        point meta rel=per plot,
        visualization depends on={x \as \xvalue},
        scatter/@pre marker code/.code={%
            \ifx\pgfplotspointmeta\pgfplots@metamin
                \def\markopts{}%
                \coordinate (minimum);
                \node [min node] {
                    \pgfmathprintnumber[fixed]{\xvalue},%
                    \pgfmathprintnumber[fixed]{\pgfplotspointmeta}
                };
            \else
                \def\markopts{mark=none}
            \fi
            \expandafter\scope\expandafter[\markopts,every node near coord/.style=green]
        },%
        scatter/@post marker code/.code={%
            \endscope
        },
        scatter,
    },
    mark max/.style={
        point meta rel=per plot,
        visualization depends on={x \as \xvalue},
        scatter/@pre marker code/.code={%
        \ifx\pgfplotspointmeta\pgfplots@metamax
            \def\markopts{}%
            \coordinate (maximum);
            \node [max node] {
                \pgfmathprintnumber[fixed]{\xvalue},%
                \pgfmathprintnumber[fixed]{\pgfplotspointmeta}
            };
        \else
            \def\markopts{mark=none}
        \fi
            \expandafter\scope\expandafter[\markopts]
        },%
        scatter/@post marker code/.code={%
            \endscope
        },
        scatter
    }
}
\makeatother

\begin{document}

\begin{tikzpicture}
    \begin{axis}[
    xtick={0,...,7},
    domain=0:7,
    axis lines*=middle,after end axis/.code={
        \draw [thick, dashed, gray] (maximum) --({axis cs:0,0}-|maximum);
    }
    ]       
    \addplot +[mark max] plot {0.001826*x^4-0.02873*x^3+0.1066*x^2+0.03454*x+0.003613};
    \end{axis}
\end{tikzpicture}

\begin{tikzpicture}
    \begin{axis}[
    xtick={0,...,7},
    domain=0:7,
    axis lines*=middle
    ]       
    \addplot +[mark min] plot {0.001826*x^4-0.02873*x^3+0.1066*x^2+0.03454*x+0.003613};
    \end{axis}
\end{tikzpicture}

\begin{tikzpicture}
    \begin{axis}[
        after end axis/.code={
            \draw [thick, dashed, gray] (maximum) --({rel axis cs:0,0}-|maximum);
        }
    ]
    \addplot +[mark max] plot {0.001826*x^4-0.02873*x^3+0.1066*x^2+0.03454*x+0.003613};
    \end{axis}
\end{tikzpicture}

\begin{tikzpicture}
    \begin{axis}
    \addplot +[mark min] plot {0.001826*x^4-0.02873*x^3+0.1066*x^2+0.03454*x+0.003613};
    \end{axis}
\end{tikzpicture}



\end{document}

[Tex/LaTex] pgfplots: scatter plot with interpolation

Let me try to summarize what I gathered from your question and from your comments:

you have some 3d visualization which requires lots of time.
"lots of" means 1000+ data points. This corresponds to a resolution of ~ 30x30
you are wondering how to improve speed; and scatter plots appeared to be a solution.

First, concerning (3.): if you need scatter plots, there is not much choice, I guess. But if you really have the choice, you should stick with surf, shader=interp. This surface plot handler can be processed efficiently by pgfplots; it is much faster than scatter plots and it results in a smaller pdf. And: if you have a relatively smooth function, it requires few data points.

Concerning the need to improve compilation times: I think there are three choices:

choice 1: the external library. Write

 \usetikzlibrary{external}
 \tikzexternalize

into your preamble; then compile with pdflatex -shell-escape. This allows automatic export of individual pictures to pdf, with sophisticated logic to preserve scaling, alignment, bounding boxes, labels, etc. You can find lots of instructions in the manual or on this site.

choice 2: the standalone package can also be used. Details in the manual or on this site.

choice 3: if even the compilation of these external pdfs takes too long, you can consider reducing the sampling resolution. Perhaps this is feasible.

If the quality degenerates but you know that you surface is smooth, you could even resort to the patchplots lib of pgfplots and use some higher-order shader (patch type=bilinear or patch type=biquadratic or patch type=bicubiccombined withshader=interp). Except forpatch type=bilinear, these patches require changes to your sampling routine (i.e. the expected input changes). See alsopatch type sampling` in pgfplots 1.7.

choice 4: you can resort to \addplot graphics. The \addplot graphics switch, however, should be regarded as last hope as it involves more manual work (tuning axis limits) than desired and involves 3rd party tools (more overhead).

MWE

Response to answer addendum

Best Answer

Related Solutions

[Tex/LaTex] How to automatically mark local extrema with pgfplots and scatter

[Tex/LaTex] pgfplots: scatter plot with interpolation

Related Question