Can I use TikZ to draw a triangular graph with central node?

Question

I'm trying to use TikZ to place the 'c' in this graph in the centre of the triangle spanned by 'a','b',d'. Is there an easy way to do this, or should I be trying to use tikzpicture for this purpose?

$$\begin{tikzcd}[column sep=small]  a \arrow[dash]{dr} \arrow[dash]{dd} \arrow[dash]{drr}& & \\
    & c \arrow[dash]{r}& d  \\
    b \arrow[dash]{ur} \arrow[dash]{urr}&&
    \end{tikzcd}$$

Welcome to TeX.SX! Please help us (and also you) and add a minimal working example (MWE), that illustrates your problem. Reproducing the problem and finding out what the issue is will be much easier when we see compilable code, starting with \documentclass and ending with \end{document}. — Bobyandbob, Nov 03 '17 at 10:00
Unrelated: Don't use $$ .. $$ for displayed math in LaTeX, see Why is \[ … \] preferable to $$?. Use \[ ... \] instead. — Torbjørn T., Nov 03 '17 at 12:41
@Bobyandbob, thank you for your advice. That makes sense, thanks. :) — Edward ffitch, Nov 03 '17 at 16:15
@TorbjørnT., thank you too for your advice, I'm still relatively new to LaTeX, so ironing out these bad habits early on is really helpful in the long run. :) — Edward ffitch, Nov 03 '17 at 16:17

JLDiaz · Answer 1 · 2017-11-03T12:38:50.287

What about inserting one extra column between c and d?

\documentclass{article}
\usepackage{tikz}
\usepackage{tikz-cd}
\begin{document}
$$\begin{tikzcd}[column sep=small]  
 a \arrow[dash]{dr} \arrow[dash]{dd} \arrow[dash]{drrr} & & \\
             & c \arrow[dash]{rr} & & d  \\
 b \arrow[dash]{ur} \arrow[dash]{urrr}&&
 \end{tikzcd}$$
\end{document}

However, this is not an equilateral triangle, nor c is at the true center. For this case I would prefer to use a tikzpicture:

\begin{tikzpicture}
    \node (c) {$c$};
    \foreach \angle/\name in {0/d,120/a,240/b}
      \node (\name) at (\angle:1) {$\name$};
    \draw (a) -- (d) -- (b) -- (a);
    \foreach \name in {a,b,d} \draw (c) -- (\name);
\end{tikzpicture}

Compare the three versions:

If (a) and (b) are not required to be vertically aligned, I would prefer to make horizontal the edge (b)--(d), which gives a better optical impression of (c) being at center:

This can be easily achieved by changing the angles in the tikzpicture version:

\begin{tikzpicture}
    \node (c) {$c$};
    \foreach \angle/\name in {-30/d,90/a,210/b}
      \node (\name) at (\angle:1) {$\name$};
    \draw (a) -- (d) -- (b) -- (a);
    \foreach \name in {a,b,d} \draw (c) -- (\name);
\end{tikzpicture}

Can I use TikZ to draw a triangular graph with central node?

1 Answers1