Name of shapes defined in an array

Question

I am trying to use labels defined in an array using tikz for drawing a path between two shapes. I have tried to use pgfmathparse but it seems not well defined for string. My syntax is probably wrong.

MWE:

\documentclass[]{standalone}
\usepackage{tikz}

\begin{document}
\def\stA {AA}
\def\stB {BB}
\def\stC{{"AA","BB"}}
\begin{tikzpicture}
\node at (0,0) (AA){coucou};
\node at (2,0) (BB){ahah};

\draw (\stA)--(\stB);

\draw (\pgfmathparse{\stC[2]}\pgfmathresult)--(\pgfmathparse{\stC[1]}\pgfmathresult);
\end{tikzpicture}
\end{document}

I can not understand, what you like to achieve. For connecting two shapes it is sufficient to say: \node (AA) at (0,0) {coucou}; \node (BB) at (2,0) {ahah}; \draw (AA) -- (BB); Syntax of this lines in your MWE is wrong as well second line with \draw, where you use TikZ math engine. What is purpose of this line? — Zarko, Jun 21 '15 at 20:02
I use an external script based on MATLAB for generating the connections of my graph. Thus I define an array of the connections. — Guuk, Jun 21 '15 at 21:27
Meanwhile I seen from both answers, what is the intention of question. Thank you for comment. — Zarko, Jun 21 '15 at 21:51

score 4 · Accepted Answer · answered Jun 21 '15 at 20:13

Here are two methods. The first one use \pgfextra to evaluate the array before to use \pgfmathresult. The second use math library to evaluate the array.

\documentclass[tikz]{standalone}
\usetikzlibrary{math}

\begin{document}
  \def\stC{{"AA","BB"}}

  \begin{tikzpicture}
    \node at (0,0) (AA){coucou};
    \node at (2,0) (BB){ahah};
    \draw (AA)--(BB);

    % method one
    \draw[red,bend left] \pgfextra{\pgfmathparse{\stC[0]}}(\pgfmathresult)
                         \pgfextra{\pgfmathparse{\stC[1]}} to (\pgfmathresult);

    % method two
    \tikzmath{\first= \stC[0]; \second = \stC[1];}
    \draw[blue, bend right] (\first) to (\second);
  \end{tikzpicture}
\end{document}

enter image description here

Note: The array index starts with 0.

A slightly different approach for method two with the evaluate key: \draw[evaluate={\first=\stC[0]; \second = \stC[1];}] (\first) to (\second); — Qrrbrbirlbel, Jun 21 '15 at 20:42

Qrrbrbirlbel · Answer 2 · 2022-09-26T15:32:18.863

3

TikZ expects fully expandable input in coordinates and such things.
See for example (there are probably more):

With the .evaluated key handler and the node coordinate system used explicitly you can do:

\draw (node cs: name/.evaluated=\stC[1])
   -- (node cs: name/.evaluated=\stC[0]);

For actual coordinates (i.e. no node names), TikZ throws everything in PGFmath anyway, and you can just do

\newcommand*\stDA{{.5,2,3.4,-1.5}}
\newcommand*\stDB{{2,1.5,3,-1}}
\foreach \da in {0,2}
  \foreach \db in {0,2}
    \draw (\stDA[\da], \stDB[\db]) -- (\stDA[\da+1], \stDB[\db+1]);

edited Sep 26 '22 at 15:32

answered Jun 21 '15 at 20:46

Qrrbrbirlbel

119,821

2

By the way, \pgfmathparse{<stuff>}\pgfmathresult can otherwise shortened to \pgfmathprint{<stuff>}. (There's also \pgfmathprintnumber.) – Qrrbrbirlbel Jun 21 '15 at 20:48
Since 2019, PGFkeys comes with its own .evaluated key that uses the same definition (apart from some checks that PGFmath is actually loaded) as .pgfmath from my previous answer. – Qrrbrbirlbel Sep 26 '22 at 15:32

Name of shapes defined in an array

2 Answers2

Linked