# Draw a spiral like an ellipse

I am trying to draw the following diagram in latex:

I find the following command :

\documentclass{article}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
\draw [domain=0:25.1327,variable=\t,smooth,samples=75]
plot ({\t r}: {0.002*\t*\t});
\end{tikzpicture}

\end{document}


But it's like a circle. Can anyone help me?

• Could you please provide with us the equation of that spiral?
– zyy
Dec 11, 2018 at 0:11
• It's phase plane portrait of differential equations, x'=Ax that A=[matrix 2x2]. for more details please check the link @zyy Dec 11, 2018 at 0:56
• @Mohammad Could you please provide with us the equation of that spiral?
– user30471
Dec 11, 2018 at 1:03
• @Andrew This is the formula [formula][1] [1]: chart.googleapis.com/… Dec 11, 2018 at 1:28

Your code shows a circular spiral because you punch in a circular spiral. Try e.g.

\documentclass{article}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
\draw [rotate=-45]
plot[domain=0:25.1327,variable=\t,smooth,samples=75] ({\t r}: {0.002*\t*\t} and {0.004*\t*\t} );
\end{tikzpicture}

\end{document}


And to add the axes and the arrow, you could use

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}

\begin{tikzpicture}
\draw[-stealth] (-3,0) -- (3,0) node[below]{$x$};
\draw[-stealth] (0,-3) -- (0,3) node[left]{$y$};
\draw [rotate=-45,postaction=decorate,decoration={markings,
mark=at position 0.93 with {\arrow{latex}}}]
plot[domain=0:32,variable=\t,smooth,samples=75] ({\t r}: {0.002*\t*\t} and {0.004*\t*\t} );
\end{tikzpicture}

\end{document}


– user121799
Dec 11, 2018 at 2:20

A PSTricks solution only for comparison and future purposes.

\documentclass[pstricks,border=12pt,12pt]{standalone}
\usepackage{pst-plot}
\begin{document}
\pspicture[algebraic,plotpoints=500](-4,-4)(4,4)
\rput{-45}(0,0){\psparametricplot[arrows=->]{0}{Pi 15 mul}{t^2*cos(t-Pi/3)/1000|2*t^2*sin(t-Pi/3)/1000}}
\endpspicture
\end{document}


• The quadratic growth is randomly or blindly chosen. Dec 11, 2018 at 7:09