# How to LaTeX the graph of a permutation?

Trying to LaTeX the graph generated by something like
Permutation([3,1,2]).show() The command latex(Permutation([3,1,2]).show())
returns the graph followed by \mathrm{None}

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Unfortunately, p.show computes the graph internally and just outputs the figure output. Put, we can do it from scratch:

sage: p = Permutation([3,1,2])
sage: edges = list(enumerate(p,start=1))
sage: d = DiGraph(edges, format='list_of_edges', loops=True)
sage: d
Looped digraph on 3 vertices
sage: latex(d) # prints the latexoutput in the default tikz
sage: view(d) # opens the pdf in a viewer


There is another way to use graphviz + dot2tex, but I always forget how to do it. Personnaly, I like to use the TikzPicture class from my package which sets up properly the options to use graphviz + dot2tex to constructs the tikzpicture:

sage: from slabbe import TikzPicture
sage: tikz = TikzPicture.from_graph(d)
sage: print(tikz)
\documentclass[tikz]{standalone}
\standaloneconfig{border=4mm}
\usepackage{amsmath}
\begin{document}
\begin{tikzpicture}[>=latex,line join=bevel,]
%%
\node (node_0) at (23.0bp,104.5bp) [draw,draw=none] {$1$};
\node (node_2) at (6.0bp,55.5bp) [draw,draw=none] {$3$};
\node (node_1) at (23.0bp,6.5bp) [draw,draw=none] {$2$};
\draw [black,->] (node_0) ..controls (18.571bp,91.254bp) and (14.669bp,80.466bp)  .. (node_2);
\draw [black,->] (node_1) ..controls (23.0bp,27.341bp) and (23.0bp,65.653bp)  .. (node_0);
\draw [black,->] (node_2) ..controls (10.429bp,42.254bp) and (14.331bp,31.466bp)  .. (node_1);
%
\end{tikzpicture}
\end{document}
sage: tikz.pdf()                        # opens up a viewer
sage: tikz.pdf('filename.pdf')   # saves the pdf file


To install those optional packages, you do:

sage -i dot2tex
sage -pip install slabbe


At some point, I might move the TikzPicture code from my package to sage. Is this something you would like for instance?

more

Not specifically as the graphs are just for illustration in a larger text document, so I just cut/paste the LaTeX output. I implemented it as def pgraph(perm): ## permutation graph amenable to latex return DiGraph([(i+1, perm[i]) for i in range(len(perm))], loops=True)

Slightly annoying indeed: the show method for a permutation

• computes a graph corresponding to that permutation
• displays it
• but does not return it

Instead it returns nothing, which in Python amounts to returning None.

That method should be decomposed into a method that provides the graph and a method that shows it.

Here is a workaround until such a method is provided.

One can check what the show method does by inspecting the source code:

sage: p = Permutation([3, 1, 2])
sage: p.show??


This helps us figure out how to produce the graph.

sage: p = Permutation([3, 1, 2])
sage: g = DiGraph([(i+1, p[i]) for i in range(len(p))], loops=True)
sage: g
Looped digraph on 3 vertices


Now we can get the LaTeX TikZ code for it:

sage: latex(g)

\begin{tikzpicture}
\definecolor{cv0}{rgb}{0.0,0.0,0.0}
\definecolor{cfv0}{rgb}{1.0,1.0,1.0}
\definecolor{clv0}{rgb}{0.0,0.0,0.0}
\definecolor{cv1}{rgb}{0.0,0.0,0.0}
\definecolor{cfv1}{rgb}{1.0,1.0,1.0}
\definecolor{clv1}{rgb}{0.0,0.0,0.0}
\definecolor{cv2}{rgb}{0.0,0.0,0.0}
\definecolor{cfv2}{rgb}{1.0,1.0,1.0}
\definecolor{clv2}{rgb}{0.0,0.0,0.0}
\definecolor{cv0v2}{rgb}{0.0,0.0,0.0}
\definecolor{cv1v0}{rgb}{0.0,0.0,0.0}
\definecolor{cv2v1}{rgb}{0.0,0.0,0.0}
%
\Vertex[style={minimum size=1.0cm,draw=cv0,fill=cfv0,text=clv0,shape=circle},LabelOut=false,L=\hbox{$1$},x=1.6204cm,y=5.0cm]{v0}
\Vertex[style={minimum size=1.0cm,draw=cv1,fill=cfv1,text=clv1,shape=circle},LabelOut=false,L=\hbox{$2$},x=0.0cm,y=0.0cm]{v1}
\Vertex[style={minimum size=1.0cm,draw=cv2,fill=cfv2,text=clv2,shape=circle},LabelOut=false,L=\hbox{$3$},x=5.0cm,y=1.1015cm]{v2}
%
\Edge[lw=0.1cm,style={post, bend right,color=cv0v2,},](v0)(v2)
\Edge[lw=0.1cm,style={post, bend right,color=cv1v0,},](v1)(v0)
\Edge[lw=0.1cm,style={post, bend right,color=cv2v1,},](v2)(v1)
%
\end{tikzpicture}


This might print a couple of warnings about required LaTeX packages.

The urls for them are outdated, see instead

Updating those links in the warnings and in the LaTeX tutorial is tracked at

more

Thanks --- I implemented the graph viewer as def pgraph(perm): ## permutation graph amenable to latex return DiGraph([(i+1, perm[i]) for i in range(len(perm))], loops=True)

I implemented the graph of a permutation function amenable to TeX as:

def pgraph(perm):
return DiGraph([(i+1, perm[i]) for i in range(len(perm))], loops=True)


It would be nice to be able to adapt it to specific representations such as

Permutation([3,1,2]).show(representation = "braid")