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From: Ulrich D i e z <ud.usenetcorrespondence@web.de>
Newsgroups: comp.text.tex
Subject: Re: [LaTeX][PGF/TikZ] Undefined control sequence error for PGF
 intersections.
Date: Mon, 2 Sep 2024 06:25:49 +0200
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Annada Behera wrote:

> Consider this minimal working example. I have two functions, f(x) = x
> and g(x) = x+sin(x). I want to draw them with PGF and at the intersection
> points, I want put black dots. Here is the TikZ code,

I just realized that inside TikZ-paths you can use \pgfextra{...}
for having LaTeX carry out arbitrary LaTeX code.
You can use this for making \t a global macro:


%\errorcontextlines=10000
\documentclass{standalone}
\usepackage{tikz, amsmath}
\usetikzlibrary{intersections}

\begin{document}

\begin{tikzpicture}

% Plots
\draw[very thick, smooth, samples=20, domain=-6.28:6.28]
     [red,  name path=line] (0,0) plot (\x, \x);
\draw[very thick, smooth, samples=20, domain=-6.28:6.28]
     [blue, name path=sine] (0,0) plot (\x, {\x + sin(\x r)});

% Draw the dots and use \pgfextra for globally saving \t:
\fill [name intersections={of=line and sine, name=i, total=\t},
       fill=green,  draw=black, thin]
       foreach \n in {1,...,\t} {(i-\n) circle (2pt)}
       \pgfextra{\global\let\t\t};

% Draw dashed lines
\foreach \n in {1,...,\t} {
    \draw[dashed] ({i-\n}) -- (0,0 -| {i-\n});
}


% Axes
\draw [<->](-6.28, 0) -- (6.28, 0);
\draw [<->](0, -6.28) -- (0, 6.28);

\end{tikzpicture}

\end{document}



Sincerely

Ulrich