Using methods like this one (and with more details here) can be useful when one tries to draw "free" curves. However, once a free curve is obtained it can be very useful to access arbitrary points on it. Unfortunately, the following naive approach is useless:
\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
\draw[->] (-2,0) -- (2,0);
\draw[->] (0,-2) -- (0,2);
\draw[thick,mark=ball] plot [smooth,tension=1.5] coordinates{(1,1) (1.4,0.5) (0.4,-0.2) (0.6,-0.2) (0.2,-1.4) (-0.5,-1.1) (-1,-1.6) (-1.4,0.4)}
node[pos=0.5]{A} node[pos=0.9]{B};
\end{tikzpicture}
\end{document}
since it yields the following:
So what is the right way to specify points on a curve generated as above?
smoothoption. It has so many interferences with other options. For further info you might want to have a look at my answer to Add arrows to a smooth tikz function. – Henri Menke Apr 11 '14 at 08:48