%
% tikztemplate.tex -- template for standalon tikz images
%
% (c) 2021 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
%
\documentclass[tikz]{standalone}
\usepackage{amsmath}
\usepackage{times}
\usepackage{txfonts}
\usepackage{pgfplots}
\usepackage{csvsimple}
\usetikzlibrary{arrows,intersections,math}
\begin{document}
\def\skala{2}
\begin{tikzpicture}[>=latex,thick,scale=\skala]

\pgfmathparse{-exp(-1)}
\xdef\l{\pgfmathresult}

\draw[->] (-0.5,0) -- (3.5,0) coordinate[label={$x$}];
\draw[->] (0,{-1-0.1/\skala}) -- (0,1.5) coordinate[label={$y$}];
\node at (0,0) [below right] {$0$};

\begin{scope}
\clip (-0.4,-1) rectangle (3.4,1.5);
\draw[color=red,line width=2.0pt] plot[domain=-1:1.1] ({\x*exp(\x)},{\x});
\end{scope}

\node[color=red] at (1.5,1) {$y=W(x)=W_0(x)$};

\draw[line width=0.3pt] ({\l},0) -- ({\l},-1);
\draw ({\l},{-0.1/\skala}) -- ({\l},{0.1/\skala});
\node at ({\l},0) [above left] {$-1/e$};

\draw (1,{-0.1/\skala}) -- (1,{0.1/\skala});
\node at (1,0) [below] {$1$};
\draw (2,{-0.1/\skala}) -- (2,{0.1/\skala});
\node at (2,0) [below] {$2$};
\draw (3,{-0.1/\skala}) -- (3,{0.1/\skala});
\node at (3,0) [below] {$3$};
\draw ({-0.1/\skala},1) -- ({0.1/\skala},1);
\node at (0,1) [left] {$1$};

\begin{scope}[xshift=-2cm,yshift=1.5cm]
\draw[->] (-0.8,0) -- (0.5,0) coordinate[label={$x$}];
\draw[->] (0,-3) -- (0,0.4) coordinate[label={left:$y$}];;
\node at (0,0) [below right] {$0$};
\draw[line width=0.3pt] ({\l},0) -- ({\l},-1);
\draw ({\l},{-0.1/\skala}) -- ({\l},{0.1/\skala});
\draw[color=blue,line width=2.0pt] plot[domain=-3:-1] ({\x*exp(\x)},{\x});
\draw ({-0.1/\skala},-1) -- ({0.1/\skala},-1);
\draw ({-0.1/\skala},-2) -- ({0.1/\skala},-2);
\node at (0,-1) [right] {$-1$};
\node at (0,-2) [right] {$-2$};
\node[color=blue] at (-0.3,-2) [left] {$y=W_{-1}(x)$};
\node at ({\l},0) [above left] {$-1/e$};
\end{scope}

\end{tikzpicture}
\end{document}

