Split nodes (again)

Question

Using an idea posted here I'd like to draw a graph of vertices and edges using some split circular nodes (and colored differently). Unfortunately the edges are not ending nicely.

It would also be lovely if I could set teh minimum node size to 6mm instead of my hack for each vertex.

Is there anything that anybody could suggest?

Here's my MWE:

\documentclass{beamer}

\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{shapes,backgrounds,calc}


% https://tex.stackexchange.com/questions/55594/tikz-two-colored-circle-split
\makeatletter
\tikzset{circle split part fill/.style args={#1,#2}{%
 alias=tmp@name, % Jake's idea !!
  postaction={%
    insert path={
     \pgfextra{% 
     \pgfpointdiff{\pgfpointanchor{\pgf@node@name}{center}}%
                  {\pgfpointanchor{\pgf@node@name}{east}}%            
     \pgfmathsetmacro\insiderad{\pgf@x}
      %\begin{scope}[on background layer]
      %\fill[#1] (\pgf@node@name.base) ([xshift=-\pgflinewidth]\pgf@node@name.east) arc
      %                    (0:180:\insiderad-0.5\pgflinewidth)--cycle;
      %\fill[#2] (\pgf@node@name.base) ([xshift=\pgflinewidth]\pgf@node@name.west)  arc
      %                     (180:360:\insiderad-0.5\pgflinewidth)--cycle;  
      \fill[#1] (\pgf@node@name.base) ([xshift=-\pgflinewidth]\pgf@node@name.east) arc
                          (0:180:\insiderad-\pgflinewidth)--cycle;
      \fill[#2] (\pgf@node@name.base) ([xshift=\pgflinewidth]\pgf@node@name.west)  arc
                           (180:360:\insiderad-\pgflinewidth)--cycle;            %  \end{scope}   
         }}}}}  
 \makeatother  

\begin{document}

\begin{tikzpicture}
  \tikzset{every node}{minimum size=8mm}
  \node[circle split part fill={red,cyan}] (p1) at (  0:1.9) {\,\,\,\,}; 
  \node[circle split part fill={blue,magenta}] (p2) at ( 72:1.9) {\,\,\,\,};
  \node[circle split part fill={green,violet}] (p3) at (144:1.9) {\,\,\,\,};
  \node[circle split part fill={green,violet}] (p4) at (216:1.9) {\,\,\,\,};
  \node[circle split part fill={orange,pink}] (p5) at (288:1.9) {\,\,\,\,};

  \draw (p1) -- (p2);
  \draw (p1) -- (p3);
  \draw (p1) -- (p4);
  \draw (p1) -- (p5);
  \draw (p2) -- (p3);
  \draw (p2) -- (p4);
  \draw (p2) -- (p5);
  \draw (p3) -- (p5);
\end{tikzpicture}
\end{document}

Many thanks.

Answer 1

You need to add shape=circle split when creating the nodes so that the shape and its anchors are constructed correctly. Then the edges connect nicely because the appropriate anchors exist.

\documentclass[tikz,border=5pt]{standalone}

\usetikzlibrary{shapes}


% http://tex.stackexchange.com/questions/55594/tikz-two-colored-circle-split
\makeatletter
\tikzset{circle split part fill/.style args={#1,#2}{%
 alias=tmp@name, % Jake's idea !!
  postaction={%
    insert path={
     \pgfextra{%
     \pgfpointdiff{\pgfpointanchor{\pgf@node@name}{center}}%
                  {\pgfpointanchor{\pgf@node@name}{east}}%
     \pgfmathsetmacro\insiderad{\pgf@x}
      %\begin{scope}[on background layer]
      %\fill[#1] (\pgf@node@name.base) ([xshift=-\pgflinewidth]\pgf@node@name.east) arc
      %                    (0:180:\insiderad-0.5\pgflinewidth)--cycle;
      %\fill[#2] (\pgf@node@name.base) ([xshift=\pgflinewidth]\pgf@node@name.west)  arc
      %                     (180:360:\insiderad-0.5\pgflinewidth)--cycle;
      \fill[#1] (\pgf@node@name.base) ([xshift=-\pgflinewidth]\pgf@node@name.east) arc
                          (0:180:\insiderad-\pgflinewidth)--cycle;
      \fill[#2] (\pgf@node@name.base) ([xshift=\pgflinewidth]\pgf@node@name.west)  arc
                           (180:360:\insiderad-\pgflinewidth)--cycle;            %  \end{scope}
         }}}}}
 \makeatother

\begin{document}

\begin{tikzpicture}
  [every node/.style={minimum size=8mm}]
  \node[shape=circle split,circle split part fill={red,cyan}] (p1) at (  0:1.9) {\,\,\,\,};
  \node[shape=circle split,circle split part fill={blue,magenta}] (p2) at ( 72:1.9) {\,\,\,\,};
  \node[shape=circle split,circle split part fill={green,violet}] (p3) at (144:1.9) {\,\,\,\,};
  \node[shape=circle split,circle split part fill={green,violet}] (p4) at (216:1.9) {\,\,\,\,};
  \node[shape=circle split,circle split part fill={orange,pink}] (p5) at (288:1.9) {\,\,\,\,};

  \draw (p1) -- (p2);
  \draw (p1) -- (p3);
  \draw (p1) -- (p4);
  \draw (p1) -- (p5);
  \draw (p2) -- (p3);
  \draw (p2) -- (p4);
  \draw (p2) -- (p5);
  \draw (p3) -- (p5);
\end{tikzpicture}
\end{document}

EDIT

Correct syntax for specifying the minimum size of nodes. This can be specified as an option to tikzpicture as shown, as an option for a scope or on a per node basis.