I am trying to draw a simple tikz-picture including a pgf-plot and some simple tikz-graphics. I want to place a circle so that it touches a parabola at point (0,0). That works well when I use values with units for the radius and position of the center of the circle, but it seems to fail when I use relative coordinates.
Here is my MWE:
\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.12}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[scale=1]
\begin{axis}[%hide axis,
xmax=1,xmin=-1,
ymin=-1,ymax=1]
\draw (0,0)--(0,1);
\draw (0,0)--(1,0);
\addplot[gray,thin,domain=-1:1]{x^2};
\addplot[gray,thin,domain=-1:1]{-x^2};
\draw[blue] (0,1cm) circle (1cm);
\draw[gray,thin] (0,.25) circle (.25);
\end{axis}
\end{tikzpicture}
\end{document}
Any help is appreciated. Thank you in advance!