Graphics, Figures & Tables ⇒ More Fill Between Questions

[coachbennett1981]

Hey Everyone,

I have been trying to figure out how to fill in this polar graph. I need to fill the intersection of the circle and function r=4+4cos x. I have been able to fill the whole circle in, but as you can see from my graph, I am missing the fill portion from the y-axis os the graph of r. I have tried to use Stefan's suggestion from this post I created viewtopic.php?t=36181, but I can't seem to figure out the intersections properly to "fill" what I don't want in blue.

Any help would be appreciated.

Code: Select all

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\usepgfplotslibrary{fillbetween}
\usetikzlibrary{backgrounds,arrows.meta}
\pgfplotsset{
    interpret as polar/.style={
            x filter/.code=\pgfmathparse{cos(rawx)*rawy},
            y filter/.code=\pgfmathparse{sin(rawx)*rawy}
        }
}
\begin{document}
\begin{tikzpicture}[>=Triangle]
\begin{axis}[
            xtick distance=1,
            ytick distance=1,
            axis lines=center,
            axis equal image,
            enlargelimits=true,
        ]
    \addplot[name path=A,
            very thick,
            domain=0:360,
            samples=100,
            smooth,
            interpret as polar
        ] 
        (x,{4+4*cos(x)});
    \addplot[name path=B,
            very thick,
            domain=0:360,
            samples=100,
            smooth,
            interpret as polar
        ] (x,{4});
       \path[name path=axis] (axis cs:0,0) -- (axis cs:1,0);
       \begin{scope}[on background layer]
        \clip (axis cs:0,0) circle (4);
        \fill[blue!30, opacity=0.5, intersection segments={
                of=A and B, sequence={R*--L*}
            }] -- cycle;

          \fill[white, intersection segments={
                of=A and B, sequence={L2 -- R2}
            }] -- cycle;
    \end{scope}
    \node[anchor=center,label=north west:$O$] at (0,0){};
\end{axis}
\end{tikzpicture}
\end{document}

[Stefan Kottwitz]

Hi Nick,

you can fill the path between A and the axis, and clip with the circle:

Code: Select all

\begin{scope}[on background layer]
 \clip (axis cs:0,0) circle (4);
 \fill[blue!30, opacity=0.5, intersection segments={
         of= A and axis, sequence = {R*--L*}
     }] -- cycle;
\end{scope}

fill-intersection.png (31.93 KiB) Viewed 224 times

Stefan

[coachbennett1981]

Thank you! I appreciate it! For some reason ( I believe the fill is the issue) but the colors are off. (See image)

filling.png (63.5 KiB) Viewed 201 times

[Stefan Kottwitz]

I think that's because you still have a second \fill command; as you had two \fill before, I do only one \fill. It adds with opacity/transparency.

Stefan