# Tikz Circle Divided into Quadrants

I'm trying to create a circle, divided into four quadrants by a dashed "cross", where the top slice is slightly smaller than the bottom slice. I want to label the four quadrants with labels a, b, c, and d (centered inside the quadrants), as well as label the top and bottom slices.

Here is my first attempt:

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{figure}
\centering
\begin{tikzpicture}
\draw (0,0) circle (2cm);
\draw[dashed] (-2,1) -- (2,1);
\draw[dashed] (0,2) -- (0,-2);
\draw (0,1.5) node{Top Piece};
\draw (0,-0.5) node{Bottom Piece};
\draw (-1,1.5) node{$a$};
\draw (1,1.5) node{$b$};
\draw (-1,-0.5) node{$c$};
\draw (1,-0.5) node{$d$};
\end{tikzpicture}
\end{figure}
\end{document}


However it has at least a few problems:

1. It is coordinate-based, which means it doesn't scale. If I want to make my circle bigger (and I am thinking bigger would be a good idea), I would have to redraw all the lines and nodes and labels to fit the new circle;
2. The lines and circle don't intersect exactly, only approximately, which may be a consequence of #1;
3. The vertical dashed line cuts through the labels "top piece" and "bottom piece".

Should I go about creating this circle a different way? Please pardon my beginner's knowledge of Tikz. And thanks for your help!

Text can not be scaled, consequently it can happens that at scaling which shrink the picture texts will overlapping. A possible solution is that texts a, top pieces and b merge in one node. Nodes with fill will hide dashed lines:

\documentclass{article}
\usepackage{tikz}

\usepackage[active,floats,tightpage]{preview}%for showing just a picture
\setlength\PreviewBorder{1em}

\begin{document}
\begin{figure}
\centering
\begin{tikzpicture}[scale=1,
every node/.style = {inner xsep=0mm, inner ysep=1mm, fill=white}
]
\draw (0,0) circle (2cm);
\draw[densely dashed]
(150:2) -- (30:2)       (270:2) -- (90:2);
\draw (0,1.4) node[fill=white]{a Top Piece b};

With scale=2 you obtain scaled pictures, but size of nodes stay the same.
• Could you use the relsize package to scale the text as well, using a macro for the scale factors? – Erik Jun 19 '15 at 8:04
• Of course :-), but what you like to achieve with it? Change the size of fonts? If you use it, the macro should be placed before tikzpicture, for example: \relsize{3}\begin{tikzpucture}[ .... <options> ...]. Matter of taste. – Zarko Jun 19 '15 at 9:22
• @Zarko You can use scale=2,transform shape, to also scale the font size. – Gonzalo Medina Jun 19 '15 at 16:26
• Thanks so much @Zarko ! Is it possible to center the a, b, c and d text in the center of the four quadrants? – Mathemanic Jun 19 '15 at 16:50