[Tex/LaTex] How to draw a spiral in phase portrait


I am aware of easily drawing a spiral in the note of nonlinear dynamics.
Here are some examples:

enter image description here

enter image description here

Best Answer

You can use TikZ. Here is an example:

enter image description here

But I never used it before, so maybe there is a better method than gluing arrows together, here is the code:


%for arrows in the middle of the line
  mark=at position #1 with {\arrow{>}}},postaction={decorate}}}

  %straight lines
  \draw[->-=.4] (0,0) to (-1,0);
  \draw[->-=.6] (0,-1) to (0,0); 
  %arcs on the left
  \draw[->-=.5] (-0.3,1) to [out=-90,in=0] (-1,0.3);
  \draw[->-=.5] (-0.3,-1) to [out=90,in=0] (-1,-0.3);
  %big circle from the bottom to the top
  \draw[->-=.5] (0.3,-1) to [out=90,in=200] (0.8,-0.3);
  \draw (0.8,-0.3) to [out=20, in =-90] (1.5,0.5) to [out=90, in=0] (0.7,1.3) to [out=180,in=90] (0,0.5);
  \draw[->-=.2]  (0,0.5) to (0,0);
  %inward spiral
  \draw[->-=.8]  (0,0) to (0.5,0);
  \draw[->] (0.5,0) to [out=0, in=-90] (1.1,0.5) to [out=90, in=0] (0.7,0.9) to [out=180, in=90] (0.4,0.6) to [out=-90, in=180] (0.6,0.4) to [out=0,in=-90] (0.75,0.6);

Check you the very minimal introduction to TikZ. In order to get the arrows in the middle of a line, I googled "tikz arrows in the middle of line".