I want to draw something like the hand-drawn picture I have attached (the second picture). This is actually a portion of the line digraph of Figure 2 (with a specified orientation), which I have also attached. I realise that I need to use a few for-each loops, but I am not sure how to draw directed edges in a for-each loop. I apologise that I am not attaching any code, but I am quite stumped as to how to even begin.
Thank you in advance.
Here is something to start with. Major steps:
postaction, drawing the "semicircle" and the filled circles is easy enoughpolar coorinates makes it easy, remembering the 3 coordinates A, B and Carc takes 3 parameters after moving to its start position: (startAngle:endAngle:radius)decorations.markings libCertainly, some code parts can further be refactored into some foreach loops.
Unfortunately I didn't succeed to move the whole drawing into a \pic. Once that works, it's easy to:
\pic or specifying them explicitely
\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
[decoration={
markings,
mark=between positions 0.06 and 1 step 5.3mm with {\arrow{stealth}}
}]
% ~~~ "semicircle" ~~~~~~~~~~
\draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5) coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
% ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\draw [fill=white] (150:1) circle [radius=1pt];
\draw [fill=white] (120:1) circle [radius=1pt];
\draw [fill=white] (90:1) circle [radius=1pt];
\draw [fill=white] (60:1) circle [radius=1pt];
\draw [fill=white] (30:1) circle [radius=1pt];
\draw [fill=white] (A) circle [radius=1pt];
\draw [fill=white] (B) circle [radius=1pt];
\draw [fill=white] (C) circle [radius=1pt];
\end{tikzpicture}
\end{document}
Finally, here's the code refactoring the placement of filled circles:
\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
[decoration={
markings,
mark=between positions 0.06 and 1 step 5.3mm with {\arrow{stealth}}
}]
% ~~~ "semicircle" ~~~~~~~~~~
\draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5) coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
% ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% refactored
\foreach \p in {(150:1),(120:1),(90:1),(60:1),(30:1),(A),(B),(C)}{
\draw [fill=white] \p circle [radius=1pt];
}
\end{tikzpicture}
\end{document}
As Jasper commented, the path for the semicircles should be split at least here:
... coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) ...
where I continued with the last 3 points for pure lazyness. Defining a second decoration style to better place the arrows there may be an option, too. It also may be a good choice to start the "semicircle" one point earlier, i.e. before the arc, i.e. at the lower left corner. Might have some beneficial consequences.
Turns out, you can split the decoration style, too; the lower left point is critical, as two pathes run through it:
\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
[decoration={
markings,
mark=between positions 0.06 and .5 step 5.3mm with {\arrow{stealth}} ,
mark=between positions 0.6 and .8 step 6mm with {\arrow{stealth}} ,% new
mark=between positions 0.835 and 1 step 6mm with {\arrow{stealth}}% new
}]
% ~~~ "semicircle" ~~~~~~~~~~
\draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5) coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
% ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% refactored
\foreach \p in {(150:1),(120:1),(90:1),(60:1),(30:1),(A),(B),(C)}{
\draw [fill=white] \p circle [radius=1pt];
}
\end{tikzpicture}
\end{document}
You could make use of \pics and then easily place and connect them.
Extending MS-SPO's nice answer:
\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\tikzset{
pics/incomplete semicircle/.style={
code={
\tikzset{
incomplete semicircle/.cd,
#1,
arrow decoration outer/.style={
decoration={
markings,
mark={at position 0.08 with {\arrow{stealth}}},
mark={at position 0.20 with {\arrow{stealth}}},
mark={at position 0.32 with {\arrow{stealth}}},
mark={at position 0.44 with {\arrow{stealth}}},
mark={at position 0.57 with {\arrow{stealth}}},
mark={at position 0.76 with {\arrow{stealth}}},
mark={at position 0.95 with {\arrow{stealth}}}
},
postaction={decorate}
},
arrow decoration inner/.style={
decoration={
markings,
mark={at position 0.3 with {\arrow{stealth}}},
mark={at position 0.8 with {\arrow{stealth}}}
},
postaction={decorate}
}
}
\coordinate (-A) at (150:1);
\coordinate (-B) at (120:1);
\coordinate (-C) at (90:1);
\coordinate (-D) at (60:1);
\coordinate (-E) at (30:1);
\coordinate (-F) at (0:.5);
\coordinate (-G) at (90:.5);
\coordinate (-H) at (0:-.5);
\draw[incomplete semicircle/arrow decoration outer]
(-A) arc[start angle=150, end angle=30, radius=1] --
(-F) -- (-H) -- cycle;
\draw[incomplete semicircle/arrow decoration inner]
(-H) -- (-G) -- (-F);
\foreach \p in {A,B,...,H}{
\node[circle, draw, fill=white, inner sep=0.75pt]
(-n\p) at (-\p) {};
}
}
},
arrowed/.style={
decoration={
markings,
mark={at position 0.55 with {\arrow{stealth}}}
},
postaction={decorate}
}
}
\begin{document}
\begin{tikzpicture}
\pic (c1) at (0,0) {incomplete semicircle};
\pic (c2) at (2,0) {incomplete semicircle};
\draw[arrowed] (c1-nF) -- (c2-nH);
\draw[arrowed] (c2-nA) -- (c1-nF);
\end{tikzpicture}
\end{document}
\pic command, such as: \pic[line width=0.2pt] (c1) at (0,0) {incomplete semicircle};. However, 2pt will be too thick for the above picture, I think.
– Jasper Habicht
Jan 19 '24 at 12:32