[Tex/LaTex] Change color of \addplot in a \foreach loop (pgfplots)

foreachpgfplots

I have this pgfplots plot and I want every single graph to have a different color. A gradient from red to blue or something else (m=2 should be red, m=11 should be blue and all the other m should be between this).

I need this to work even when I change the amount of graphs.

I already tried to transfer the code lines from this example, but I can't get it working: Plotting a graph with several values of a parameter

The minimum working example is added below.

Thank you.

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{pgfplots}    
\pgfplotsset{compat=newest}

\pgfplotsset{
    gainplot/.style={
        axis x line*=box,
        xmax=10,
        xmin=0.1,
        xmode=log,
        width=14cm,
        xlabel=$F_\textup{x}$,
        xticklabel style={yshift=-0.2cm,},
        xtick={0.1,1.0,10.0},
        xticklabels={{$0.1$},{$1.0$},{$10.0$}},
        axis y line*=box,
        ymax=3,
        ymin=0,
        ymode=normal,
        height=7cm,
        ylabel=$K$,
        yticklabel style={xshift=-0.2cm,},
        ytick={0,1,2,3 },
        yticklabels={{$0$},{$1$},{$2$},{$3$}},
        grid = both,
        grid style={line width=0.2pt,},
        legend style={
            font=\scriptsize,
            at={(0.5,1.03)},
            anchor=south,
            draw=none,
        },
        legend columns=5,
    },
    gainplot/.belongs to family=/pgfplots/scale,
}

\pgfmathdeclarefunction{gaincurve}{2}{%
    \pgfmathparse{%
        (x^2*(#2-1)/(sqrt((#2*x^2-1)^2+x^2*(x^2-1)^2*(#2-1)^2*#1^2)))
    }%
}

\tikzstyle{gaincurvestyle}=[
    smooth,
    %thick,
    mark=none,
    domain=0.1:10,
    samples=100,
]


\begin{document}

\begin{figure}[]
\centering

\begin{tikzpicture}
\begin{axis}[gainplot]
\foreach \m in {2,3,...,11}{
    \addplot[gaincurvestyle,red]{gaincurve(0.2,\m)}; %%% Here help is needed.
    \addlegendentryexpanded{$m=\m$}
}
\end{axis}
\end{tikzpicture}

\caption{Placeholder.}
\end{figure}

\end{document}

Best Answer

You can use the \edef trick mentioned in the pgfplots manual, combined with evaluate in the \foreach, and the red!<value>!blue color syntax.

If you want to normalize based on the values of the loop, you can use

\foreach [evaluate=\m as \redfrac using (\m-<minimum>)*100/(<maximum>-<minimum>)] ...

and then set the color of the plot to red!\redfrac!blue. For example, if the lowest value in the loop is 2 and the highest is 11, as in your example, you use (\m-2)*100/(11-2).

If you instead want to normalize based on the index of the loop, you can do

\foreach [count=\i from 0,evaluate=\i as \redfrac using \i*100/<number of elements in list>)] ...

For example, if you're looping over a list of 15 values, use \i*100/15. In both cases, it's just a matter of normalizing a value so that it runs from 0 to 100.

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{pgfplots}    
\pgfplotsset{compat=newest}

\pgfplotsset{
    gainplot/.style={
        axis x line*=box,
        xmax=10,
        xmin=0.1,
        xmode=log,
        width=14cm,
        xlabel=$F_\textup{x}$,
        xticklabel style={yshift=-0.2cm,},
        xtick={0.1,1.0,10.0},
        xticklabels={{$0.1$},{$1.0$},{$10.0$}},
        axis y line*=box,
        ymax=3,
        ymin=0,
        ymode=normal,
        height=7cm,
        ylabel=$K$,
        yticklabel style={xshift=-0.2cm,},
        ytick={0,1,2,3 },
        yticklabels={{$0$},{$1$},{$2$},{$3$}},
        grid = both,
        grid style={line width=0.2pt,},
        legend style={
            font=\scriptsize,
            at={(0.5,1.03)},
            anchor=south,
            draw=none,
        },
        legend columns=5,
    },
    gainplot/.belongs to family=/pgfplots/scale,
}

\pgfmathdeclarefunction{gaincurve}{2}{%
    \pgfmathparse{%
        (x^2*(#2-1)/(sqrt((#2*x^2-1)^2+x^2*(x^2-1)^2*(#2-1)^2*#1^2)))
    }%
}

\tikzstyle{gaincurvestyle}=[
    smooth,
    %thick,
    mark=none,
    domain=0.1:10,
    samples=100,
]


\begin{document}

\begin{figure}[]
\centering

\begin{tikzpicture}
\begin{axis}[gainplot]
\foreach [evaluate=\m as \redfrac using (\m-2)*100/(11-2)] \m in {2,3,...,11}{
    \edef\temp{\noexpand\addplot[gaincurvestyle,red!\redfrac!blue]{gaincurve(0.2,\m)};
    \noexpand\addlegendentry{$m=\m$}}
    \temp
}
\end{axis}
\end{tikzpicture}

\caption{Placeholder.}
\end{figure}

\end{document}

Related Solutions

[Tex/LaTex] plotting two time series with bounds

This happens because PGFPlots only uses one "stack" per axis: You're stacking the second confidence interval on top of the first. The easiest way to fix this is probably to use the approach described in "Is there an easy way of using line thickness as error indicator in a plot?": After plotting the first confidence interval, stack the upper bound on top again, using stack dir=minus. That way, the stack will be reset to zero, and you can draw the second confidence interval in the same fashion as the first:

\documentclass{standalone}
\usepackage{pgfplots, tikz}

\usepackage{pgfplotstable}

\pgfplotstableread{
temps   y_h y_h__inf    y_h__sup    y_f y_f__inf    y_f__sup    

1   0.237340    0.135170    0.339511    0.237653    0.135482    0.339823    
2   0.561320    0.422007    0.700633    0.165871    0.026558    0.305184    
3   0.694760    0.534205    0.855314    0.074856    -0.085698   0.235411    
4   0.728306    0.560179    0.896432    0.003361    -0.164765   0.171487    
5   0.711710    0.544944    0.878477    -0.044582   -0.211349   0.122184    
6   0.671241    0.511191    0.831291    -0.073347   -0.233397   0.086703    
7   0.621177    0.471219    0.771135    -0.088418   -0.238376   0.061540    
8   0.569354    0.431826    0.706882    -0.094382   -0.231910   0.043146    
9   0.519973    0.396571    0.643376    -0.094619   -0.218022   0.028783    
10  0.475121    0.366990    0.583251    -0.091467   -0.199598   0.016664    
}{\table}

\begin{document}
\begin{tikzpicture}

    \begin{axis}
    % y_h confidence interval
    \addplot [stack plots=y, fill=none, draw=none, forget plot]   table [x=temps, y=y_h__inf]   {\table} \closedcycle;
    \addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend]   table [x=temps, y expr=\thisrow{y_h__sup}-\thisrow{y_h__inf}]   {\table} \closedcycle;
    % subtract the upper bound so our stack is back at zero
    \addplot [stack plots=y, stack dir=minus, forget plot, draw=none] table [x=temps, y=y_h__sup] {\table};

    % y_f confidence interval
    \addplot [stack plots=y, fill=none, draw=none, forget plot]   table [x=temps, y=y_f__inf]   {\table} \closedcycle;
    \addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend]   table [x=temps, y expr=\thisrow{y_f__sup}-\thisrow{y_f__inf}]   {\table} \closedcycle;

    % the line plots (y_h and y_f)    
    \addplot [stack plots=false, very thick,smooth,blue]  table [x=temps, y=y_h]   {\table};
    \addplot [stack plots=false, very thick,smooth,blue]  table [x=temps, y=y_f]   {\table};
    \end{axis}

\end{tikzpicture}
\end{document}

[Tex/LaTex] pgfplots: use foreach inside addplot

To avoids expansion issues with \foreach, pgfplots offers \pgfplotsinvokeforeach which can be used without problems; also, you can easily draw your lines from the curve to the axis using the function (no need to find intersections points); declaring the function from the beginning also simplifies the code:

The code:

\documentclass[border=5]{standalone}
\usepackage{pgfplots}
%\pgfplotsset{compat=1.12}

\pgfmathdeclarefunction{myfunct}{1}{%
  \pgfmathparse{(#1-5)^2 + 20}%
}

\begin{document}    
\begin{tikzpicture} 
    \begin{axis}[%
        ,axis lines=left
        ,xtick=\empty
        ,ytick=\empty
        ]
        \addplot[samples=100,domain=0:10] {myfunct(x)};
        \pgfplotsinvokeforeach{1,...,9}{
            \addplot coordinates { (#1,0) (#1,40) };}
    \end{axis}  
\end{tikzpicture}\qquad
\begin{tikzpicture} 
    \begin{axis}[%
        ,axis lines=left
        ,xtick=\empty
        ,ytick=\empty
        ]
        \addplot[samples=100,domain=0:10] {myfunct(x)};
        \pgfplotsinvokeforeach{1,...,9}{
            \addplot coordinates { (#1,0) (#1,{myfunct(#1)}) };
            \node[above=5pt] at (axis cs:#1,{myfunct(#1)}) {\pgfmathprint{myfunct(#1)}};
            }
    \end{axis}  
\end{tikzpicture}   

\end{document}

Update

Using the same idea, name the path for the curve and inside \pgfplotsinvokeforeach draw the lines and name them; find the intersection points and draw the desired lines with the required labels:

\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
\usepgfplotslibrary{fillbetween}
\pgfplotsset{compat=1.10}

\usepackage{filecontents}
\begin{filecontents*}{mydata.dat}
-6 36
-5 25
-4 16
-3 9
-2 4
-1 1
0 0
1 1
2 4
3 9
4 16
5 25
6 36
\end{filecontents*}


\begin{document}

\begin{tikzpicture}

\begin{axis}[
  axis lines=left,
  scaled ticks=false,
  xtick=\empty,
  ytick=\empty,
  ymin=0,
]
\addplot[no marks,smooth,name path=curve] table {mydata.dat};
\pgfplotsinvokeforeach{-6,...,6}{
  \addplot[draw=none,name path={line#1}] coordinates  { (#1,0) (#1,40) };
  \path[name intersections={of=curve and line#1,by={point#1}}];
  \draw[red]
    (axis cs:#1,0) -- (point#1) node[above,black] {#1};
}
\end{axis}

\end{tikzpicture}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] plotting two time series with bounds

[Tex/LaTex] pgfplots: use foreach inside addplot

Update

Related Question