Gradient colour in tikz pgfplot marker

Question

I'm trying to replicate the dual colours of the circles in this graph:

enter image description here

\documentclass[tikz,border={40pt 12pt}]{standalone}
\usepackage{pgfplots}
\usetikzlibrary{plotmarks}
\begin{document}
\begin{tikzpicture}[trim axis left,trim axis right]

\begin{axis}[%
width=4.52083333333333in,
height=1.9359375in,
scale only axis,
xmin=0,
xmax=2,
xlabel={Partition},
ymin=0,
ymax=5,
ytick={1,...,5},
xtick={0,0.5,...,2},
ylabel={No Partition}
]
\addplot [
color=red,
only marks,
mark=ball,
mark options={solid, line width=1pt},
forget plot
]
table[row sep=crcr]{
0.752891515 1.119390244\\
0.918362178 1.65402439\\
0.794259181 4.527682927\\
1.10865344 0.515142276\\
1.621612495 1.002439024\\
};
\addplot [
color=black,
dashed,
line width=1pt,
forget plot
]
table[row sep=crcr]{
0.6 2.64921945346413\\
0.7 2.44758628403132\\
0.8 2.24595311459851\\
0.9 2.04431994516571\\
1 1.8426867757329\\
1.1 1.64105360630009\\
1.2 1.43942043686729\\
1.3 1.23778726743448\\
1.4 1.03615409800167\\
1.5 0.834520928568865\\
1.6 0.632887759136058\\
};
\end{axis}
\end{tikzpicture}%
\end{document}

So far I have this:

enter image description here

Does anyone know of inbuilt gradient options for colouring? If not I'll settle for

score 7 · Accepted Answer · edited Jun 09 '17 at 16:25

You can declare your own plot marks using

\pgfdeclareplotmark{<name>}{<code that draws the marks>}

For example, you could set

\pgfdeclareplotmark{gradient}{
    \fill [
        draw=none,
        left color=red,
        right color=blue,
        shading angle=45
    ] (0,0) circle [radius=4pt];
}

Full code:

\documentclass[tikz, border=5pt]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{plotmarks}
\begin{document}
\begin{tikzpicture}

\pgfdeclareplotmark{gradient}{
    \fill [
        draw=none,
        left color=red,
        right color=blue,
        shading angle=45
    ] (0,0) circle [radius=\pgfplotmarksize];
}

\begin{axis}[%
width=4.52083333333333in,
height=1.9359375in,
scale only axis,
xmin=0,
xmax=2,
xlabel={Partition},
ymin=0,
ymax=5,
ytick={1,...,5},
xtick={0,0.5,...,2},
ylabel={No Partition}
]
\addplot [
only marks, mark=gradient, mark size=5pt
]
table[row sep=crcr]{
0.752891515 1.119390244\\
0.918362178 1.65402439\\
0.794259181 4.527682927\\
1.10865344 0.515142276\\
1.621612495 1.002439024\\
};
\addplot [
color=black,
dashed,
line width=1pt,
forget plot
]
table[row sep=crcr]{
0.6 2.64921945346413\\
0.7 2.44758628403132\\
0.8 2.24595311459851\\
0.9 2.04431994516571\\
1 1.8426867757329\\
1.1 1.64105360630009\\
1.2 1.43942043686729\\
1.3 1.23778726743448\\
1.4 1.03615409800167\\
1.5 0.834520928568865\\
1.6 0.632887759136058\\
};
\end{axis}
\end{tikzpicture}%
\end{document}

@Jake, is there an easy way of having a radial gradient and make the outer color transparent, so each point looks like a smooth point? — alfC, Oct 10 '13 at 21:12
Learning how to make it white will help, but the ultimate goal is to make the points smooth and able to partially supper impose in order to form complicated larger blobs without sharp borders. — alfC, Oct 10 '13 at 21:15
@alfC: For white, you can just do \fill [ draw=white, inner color=black, outer color=white,... (or for finer control, take a look at http://tex.stackexchange.com/q/115340/2552). I'm not sure about the transparency, though, you might want to open a new question for that. — Jake, Oct 10 '13 at 21:20

score 4 · Answer 2 · edited Jun 09 '17 at 16:26

You need first to declare a shading:

\pgfdeclarehorizontalshading{myshading}{2cm}{color(0pt)=(blue); color(2cm)=(yellow)}

And then a new marker:

\pgfdeclareplotmark{mymarker}{%
    \begin{pgfscope}
        \pgfpathcircle{\pgfpointorigin}{\pgfplotmarksize}
        \pgfusepath{clip}
        \pgfpathrectangle{\pgfpoint{-\pgfplotmarksize}{-\pgfplotmarksize}}{\pgfpoint{2\pgfplotmarksize}{2\pgfplotmarksize}}
        \pgfshadepath{myshading}{-45}
        \pgfusepath{stroke}
    \end{pgfscope}
    \pgfpathmoveto{\pgfpointorigin}
    \pgfpathcircle{\pgfpointorigin}{\pgfplotmarksize}
    \pgfusepath{stroke}
}

So your MWE should be something like this:

\documentclass[tikz,border={40pt 12pt}]{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=1.8} 

\pgfdeclarehorizontalshading{myshading}{2cm} 
    {color(0pt)=(blue); color(2cm)=(yellow)} 

\pgfdeclareplotmark{mymarker}{%
    \begin{pgfscope}
        \pgfpathcircle{\pgfpointorigin}{\pgfplotmarksize}
        \pgfusepath{clip}
        \pgfpathrectangle{\pgfpoint{-\pgfplotmarksize}{-\pgfplotmarksize}}{\pgfpoint{2\pgfplotmarksize}{2\pgfplotmarksize}}
        \pgfshadepath{myshading}{-45}
        \pgfusepath{stroke}
    \end{pgfscope}
    \pgfpathmoveto{\pgfpointorigin}
    \pgfpathcircle{\pgfpointorigin}{\pgfplotmarksize}
    \pgfusepath{stroke}
}


\begin{document}
\begin{tikzpicture}[trim axis left,trim axis right]
\begin{axis}[%
width=4.52083333333333in,
height=1.9359375in,
scale only axis,
xmin=0,
xmax=2,
xlabel={Partition},
ymin=0,
ymax=5,
ytick={1,...,5},
xtick={0,0.5,...,2},
ylabel={No Partition}
]


\addplot [
color=red,
only marks,
mark=mymarker,
forget plot
]
table[row sep=crcr]{
0.752891515 1.119390244\\
0.918362178 1.65402439\\
0.794259181 4.527682927\\
1.10865344 0.515142276\\
1.621612495 1.002439024\\
};
\addplot [
color=black,
dashed,
line width=1pt,
forget plot
]
table[row sep=crcr]{
0.6 2.64921945346413\\
0.7 2.44758628403132\\
0.8 2.24595311459851\\
0.9 2.04431994516571\\
1 1.8426867757329\\
1.1 1.64105360630009\\
1.2 1.43942043686729\\
1.3 1.23778726743448\\
1.4 1.03615409800167\\
1.5 0.834520928568865\\
1.6 0.632887759136058\\
};
\end{axis}
\end{tikzpicture}%
\end{document}

And will produce this:

result

Many thanks for your contribution! Your approach will be useful for something else I have in mind :) — HCAI, Jun 20 '13 at 18:07

Gradient colour in tikz pgfplot marker

2 Answers2