4

I am in the process of converting some old figures into Tikz, and have come across something which I'm sure Tikz must be able to manage, but haven't figured out how yet...

Target picture: Is here:

This is what I'm trying to draw

Note that there are 12 labelled edges, with each edge also having an arrow. For every edge, as I travel along the direction of the edge I see the arrow on the right (sloped in the same direction as the edge), and the label on the left (not sloped).

Here is an MWE attempt, using sloped, together with above and below:

\documentclass[tikz,border=3mm]{standalone}
\tikzset{vertex/.style={circle, draw, fill=black, inner sep=0pt, minimum width=2mm}}
\begin{document}
\begin{tikzpicture}
\foreach \x/\y [count=\i] in {0/0,3/0,1/1,2/1,1/2,2/2,0/3,3/3}
  \node[vertex] at (\x,\y) (\i) {};
\foreach \s/\t [count=\i] in {1/7,7/8,8/2,2/1,4/6,6/5,5/3,3/4,5/7,2/4,8/6,3/1}
  \path (\s) edge node[midway,above] {\footnotesize \i} node[sloped,midway,below] {$\longrightarrow$} (\t);
\end{tikzpicture}
\end{document}

This looks like this:

enter image description here

Not quite right! As well as the numbering on the edges being, literally, above the centrepoint of the edge, the arrows are also not all pointing in the right direction.

I can, of course, break up the for loops and produce a satisfactory picture, but surely Tikz has a better solution?

  • 2
    For the arrows, you could add allow upside down to the node options. – Max Sep 11 '18 at 15:06
  • 1
    allow upside down works nicely -- thank you! If I do this to the node labels too, then they're in the right places, but need to be returned to normal orientation... Does that help I wonder? – rbrignall Sep 11 '18 at 15:35
  • Maybe use auto=left for the nodes with the numbers and auto=right for the nodes with the arrows (the latter in combination with allow upside down). I can't test now unfortunately. – Max Sep 11 '18 at 16:50
5

An option using conditionals to swap the positions fo the arrows and the text depending of the the \orientation value 0 or 1 in the foreach imputs; the arrows are drawing using the midway node sloped points like node_name.east, nodename.west; to control the direction other value is added in the foreach inputs \dir, using -> and <- notations. Sorry if it is not the most elegant but controls almost everything to get the desired result.

RESULT:

enter image description here

MWE:

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{arrows.meta}
\tikzset{vertex/.style={circle, draw, fill=black, inner sep=0pt, minimum width=1.5mm}}
\begin{document}
    \begin{tikzpicture}[
        >={Stealth[length=3pt]}
    ]
    \foreach \x/\y [count=\i] in {0/0,3/0,1/1,2/1,1/2,2/2,0/3,3/3}{
        \node[vertex] at (\x,\y) (\i) {};
    }
    \foreach \s/\t/\dir/\orientation [count=\i] in {
        1/7/->/1,%1
        7/8/->/1,%2
        2/8/<-/0,%3
        1/2/<-/1,%4
        4/6/<-/0,%5
        6/5/<-/1,%6
        5/3/->/0,%7
        3/4/->/0,%8
        5/7/<-/0,%9
        2/4/<-/1,%10
        8/6/<-/0,%11
        3/1/<-/1%12
    }{
        \ifnum\orientation=0
            \draw (\s)
                -- (\t)
                node[
                minimum width=0.6cm,
                midway,
                above,
                sloped,
                label={[inner sep=2pt]-90:\scriptsize\i}
                ](temp){};
        \fi
        \ifnum\orientation=1
            \draw (\s) 
                -- (\t)
                node[
                minimum width=0.6cm,
                midway,
                below,
                sloped,
                label={[inner sep=2pt]90:\scriptsize\i}
                ](temp){};
        \fi
        \draw[\dir] (temp.west) -- (temp.east);
    }
    \end{tikzpicture}
\end{document}
  • Arrows 5 is in the opposite direction... – AndréC Sep 11 '18 at 16:41
  • Oh what a mistake, although I review for a while, thank you. – J Leon V. Sep 11 '18 at 16:52
  • Although I'm reluctant to pass more arguments, this is a good general solution. For my specific case, adding label={[inner sep=2pt]90:\scriptsize\i} as you have, together with allow upside down to the second node (and removing the first node) is a good solution. – rbrignall Sep 11 '18 at 19:24
3

This is just for fun. The arrows adjust themselves a bit to the path they get attached at.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings}
\tikzset{vertex/.style={circle, draw, fill=black, inner sep=0pt, minimum
width=2mm},arrow right/.style args={#1/#2}{postaction={decorate,decoration={markings,
mark=at position 0.5 with {%
\draw[-stealth]
(-1.5mm-\pgfdecoratedpathlength/8,{-1*#2*(1mm+min(\pgfdecoratedpathlength/16,1mm)}) -- 
(1.5mm+\pgfdecoratedpathlength/8,{-1*#2*(1mm+min(\pgfdecoratedpathlength/16,1mm)});
\node[font=\footnotesize] at (0,#2*2mm){#1};}}}}}
\begin{document}
\begin{tikzpicture}
\foreach \x/\y [count=\i] in {0/0,3/0,1/1,2/1,1/2,2/2,0/3,3/3}
  \node[vertex] at (\x,\y) (\i) {};
\foreach \s/\t/\u [count=\i] in
{1/7/1,7/8/1,8/2/1,2/1/1,6/4/1,6/5/-1,5/3/-1,3/4/-1,5/7/1,2/4/1,8/6/1,3/1/1}
  \path (\s) edge[arrow right=\i/\u] 
  (\t);
\end{tikzpicture}
\end{document}

enter image description here

0

The simplest solution might be to add auto=right to the nodes with the numbers, and allow upside down to the nodes with the arrows.

enter image description here

Not that this is not exactly the same as your example picture, because not all numbers are right of the arrow.

\documentclass[tikz,border=3mm]{standalone}
\tikzset{vertex/.style={circle, draw, fill=black, inner sep=0pt, minimum width=2mm}}
\begin{document}
\begin{tikzpicture}
\foreach \x/\y [count=\i] in {0/0,3/0,1/1,2/1,1/2,2/2,0/3,3/3}
  \node[vertex] at (\x,\y) (\i) {};
\foreach \s/\t [count=\i] in {1/7,7/8,8/2,2/1,4/6,6/5,5/3,3/4,5/7,2/4,8/6,3/1}
  \path (\s) edge node[midway,auto=right] {\footnotesize \i} node[sloped,midway,above,allow upside down] {$\longrightarrow$} (\t);
\end{tikzpicture}
\end{document}

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.