1

I want to "define" a variable inside my tikzpicture. This answer gives a solution for how to do that, using the math library.

The thing I am concerned with is that when I assign \x1 the value of 1, let's say, this value is defined globally across my latex document.

So if I want to draw two rather similar graphics, which for both it is comfortable to use the name x1 to describe a specific length, then I need to either

  • come up with a new name for this length, such as x1 and x1new
  • or I need to run over the definition for \x1=1 later in the document with \x1=2.

My question is whether there is a way to define a variable and assign it a value just for the current tikzpicture environment?

A MWE:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{math}
\tikzmath{\x1 = 2; \y1=1;} %%%% <<----- First definition
\begin{document}
In this lecture we will talk about complex numbers.

The complex number $2+\mathrm{i}$ can be pictured in the following way:


\begin{tikzpicture}
\draw[step=.5cm,gray,very thin] (-2.4,-2.4) grid (2.4,2.4);
\draw [-latex] (-2.5,0) -- (2.5,0);
\draw [-latex] (0,-2.5) -- (0,2.5);
\draw [thick, - latex] (0,0) -- (\x1,\y1);
\end{tikzpicture}


An example for a vector with a negative argument is the following:


\begin{tikzpicture}
\tikzmath{\y1=-1;}  %%%% <<----- run over the previous value of y1
\draw[step=.5cm,gray,very thin] (-2.4,-2.4) grid (2.4,2.4);
\draw [-latex] (-2.5,0) -- (2.5,0);
\draw [-latex] (0,-2.5) -- (0,2.5);
\draw [thick, - latex] (0,0) -- (\x1,\y1);
\end{tikzpicture}


\end{document}
Celdor
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tush
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1 Answers1

1

If you make your definition inside a group around your tikzpicture, it will only define the variable inside this group.

You can explicitly add a group by e.g. using {...} or you can place your definition inside the tikpicture, which automatically forms a group.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{math}
\tikzmath{\x1 = 2; \y1=1;} %%%% <<----- First definition
\begin{document}
In this lecture we will talk about complex numbers.

The complex number $2+\mathrm{i}$ can be pictured in the following way:


{
\tikzmath{\x1 = 1;}
\begin{tikzpicture}
\draw[step=.5cm,gray,very thin] (-2.4,-2.4) grid (2.4,2.4);
\draw [-latex] (-2.5,0) -- (2.5,0);
\draw [-latex] (0,-2.5) -- (0,2.5);
\draw [thick, - latex] (0,0) -- (\x1,\y1);
\end{tikzpicture}
}


An example for a vector with a negative argument is the following:


\begin{tikzpicture}
\tikzmath{\y1=-1;}  %%%% <<----- run over the previous value of y1
\draw[step=.5cm,gray,very thin] (-2.4,-2.4) grid (2.4,2.4);
\draw [-latex] (-2.5,0) -- (2.5,0);
\draw [-latex] (0,-2.5) -- (0,2.5);
\draw [thick, - latex] (0,0) -- (\x1,\y1);
\end{tikzpicture}


\end{document}
samcarter_is_at_topanswers.xyz
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