# How to plot a 2-Graph (Königsberg Graph, Euler)

I want to plot a 2-graph, the Königsberg graph. I've got this: V={A,B,C,D} the set of vertices E={e1={A,B}, e2={A,B}, e3={A,D}, e4={C,D}, e5={B,C}, e6={B,C}, e7={B,D}} the set of nodes (axis, aristas)

Thanks

• What is a 2-graph? – percusse Sep 29 '14 at 20:15
• @percusse Maybe the OP means a planar graph... – jub0bs Sep 29 '14 at 20:48
• What have you tried? Do you know of the graphs TikZ library (section 19 in the doc)? – jub0bs Sep 29 '14 at 20:51
• @percusse 2-graph is a graph where every node has got 2 axis – Tobal Oct 1 '14 at 19:50
• It's meant to emphasize that this is not a math site so it needs some context. – percusse Oct 1 '14 at 21:00

You can do that with pst-eucl, if you want to give a try at pstricks. Here is a short code, compilable with pdflatex if you use the shell-escape (TeX Live, MacTeX) or --enable-write18 (MiKTeX) switch:

\documentclass[12pt, pdf, x11names]{article}%

\usepackage{pst-eucl}

\begin{document}

\begin{pspicture*}(-1, -1.2)(2, 1.2)
\psset{linewidth=0.5pt, linecolor=SteelBlue3, fillcolor=SteelBlue3, PointNameSep=0.8em}
\pstGeonode[PointSymbol=none, PointName=none](0.5,-0.5){O1}(-0.5, -0.5){P1}(0.5,0.5){O2}(-0.5,0.5){P2}
\pstGeonode[PointSymbol=o, PosAngle={180,180,180,0}](0,-1){A}(0,0){B}(0,1){C}(1.5,0){D}
\ncline{A}{D} \ncline{B}{D} \ncline{C}{D}
\pstArcOAB{O1}{B}{A}\pstArcOAB{P1}{A}{B}
\pstArcOAB{O2}{C}{B}\pstArcOAB{P2}{B}{C}
\end{pspicture*}

\end{document} • I've got a lot of error messages with miktex2.9. I've installed all pst packages. – Tobal Sep 30 '14 at 6:32
• @Tobal: I forgot to mention that you have to launch pdflatex with the --enable-write18 switch. I suppose it's the problem. Could you confirm that, please? – Bernard Sep 30 '14 at 8:33
• this is not the problem. In a message I obtain SteelBlue3 is not defined. – Tobal Sep 30 '14 at 15:11
• Strange… It's defined in the x11names module of xcolor (p. 40 of the doc) wich is loaded by pstricks, which is loaded by pst-eucl. That's why it is among the class options (to avoid optionsloading conflicts). Just in case, load xcolor (but x11names must remain a class option). – Bernard Sep 30 '14 at 15:19
• – Bernard Sep 30 '14 at 17:47