# Parallel edges in Graph using \path

I'm trying to get Parallel edges between nodes. I recognize that very similar questions have been asked before, however;

1. Those solutions don't seem to have worked on my problem, though my search was not exhaustive. Most solutions seem to use \draw, and I don't yet have the skill to reconcile \path approach with \draw. Further, I couldn't find mention in the 3.0.0 documentation.

2. I'd like to keep this style consistent with other graphs that I have done for a report, as I already have a few examples working. If someone knows how to remove the arrow from the loop that would be very helpful also. As you can see I have tried using "stealth", but haven't had any luck.

My code so far:

\documentclass[14pt,oneside,a4paper]{report}
\usepackage{tikz}
\usetikzlibrary{arrows,decorations.pathmorphing,backgrounds,positioning,fit,petri}
\begin{document}
\begin{figure}

\sbox{\tempbox}{%
\begin{tikzpicture}[-,>=stealth',shorten >=1pt,auto,node distance=2cm,
thick,main node/.style={circle,fill=black!20,draw}]

\node[main node] (3) {$v_3$};
\node[main node] (1) [below left of=3] {$v_1$};
\node[main node] (2) [below right of=3] {$v_2$};

\path[every node/.style={font=\sffamily\small}]
(1) edge[loop left] node  {$e_{1}$} (1)
(1) edge node [left] {} (2)
(1) edge node [left] {} (3)
(2) edge node [right] {} (3);
\path [draw, line width=3] (2) |-(3);
\end{tikzpicture}
}

\begin{subfigure}{.5\textwidth}
\centering
\usebox{\tempbox}
\caption{A non-simple Graph}
\end{subfigure}%
\begin{subfigure}{.5\textwidth}
\centering
\vbox to\ht\tempbox{
\vfill
\begin{math}
A_{G} = \left(
\begin{array}{ccc}
1 & 1 & 1 \\
1 & 0 & 2 \\
1 & 2 & 0

\end{array}
\right)
\end{math}
\vfill
}
\caption{Matrix Corresponding to the Graph }
\end{subfigure}%
\caption{A graph's diagram and it's adjacency matrix representation.}
\end{figure}
\end{document}


The top Graph is of the style I'm aiming for. The Graph below it is what the code posted creates. The sharp-angled edge is the one which i'm wishing to modify to be smoother. I've tried using:

(2) edge node [bend left = 15] {} (3);


However that didn't work. NB: I really don't know what I'm doing. I included the Matrix as I'm working in a figure environment, if that is meaningful.

• Please, make your document complete, than can be copied and compiled. Also try to remove errors in use of subfigure. – Zarko Feb 3 '16 at 12:56
• Why did you add a node in the edge if it's supposed to be empty anyways? – Alenanno Feb 3 '16 at 13:11
• Maybe for future use? I was unsure about their purpose, so I didn't touch them in my answer. Instead nodes I would rather use quotas library ... – Zarko Feb 3 '16 at 13:15

Edit: In the first attempt I miss understand question, so I add arrows instead to remove it from loop. Hot to do this is described in TikZ manual on page 749 (version 3.0.1a)

Something like this?

\documentclass{article}
\usepackage{subcaption}

\usepackage{tikz}
\usetikzlibrary{arrows,positioning}

\begin{document}
\begin{figure}

\newsavebox\tempbox
\sbox{\tempbox}{%
\begin{tikzpicture}[
thick, shorten >=1pt,
auto,
node distance=2cm,
main node/.style={circle, draw, fill=black!20}
]
\node[main node] (3) {$v_3$};
\node[main node] (1) [below left =of 3] {$v_1$};% <--- se proper use of positioning
\node[main node] (2) [below right=of 3] {$v_2$};

\path[every loop/.style={}]
(1) edge[loop left,"$e_{1}$"] (1)% <-- for edge labels I use quotes library

(1) edge (2)% <-- nodes are removed since they are not used
(1) edge (3)
(2) edge (3)
(3) edge [red, bend left] (2); % <-- edge is now smooth
\end{tikzpicture}
}

\begin{subfigure}{.5\textwidth}
\centering
\usebox{\tempbox}
\caption{A non-simple Graph}
\end{subfigure}%
\begin{subfigure}{.5\textwidth}
\centering
\vbox to\ht\tempbox{
\vfill
\begin{math}
A_{G} = \left(
\begin{array}{ccc}
1 & 1 & 1 \\
1 & 0 & 2 \\
1 & 2 & 0
\end{array}
\right)
\end{math}
\vfill
}
\caption{Matrix Corresponding to the Graph }
\end{subfigure}%
\caption{A graph's diagram and it's adjacency matrix representation.}
\end{figure}
\end{document}