I am working on a paper in LaTeX and I'm trying to insert a simple decision tree diagram using TikZ. However, I am not good with TikZ and I'm having two small problems with my tree.

This is my tree right now, and I am having trouble with it in two ways:
- I would like to get rid of the extra horizontal line before the top R=0.
- I would like for the nodes to be inside of circles.
Again, I'm not good with TikZ, and can't seem to get it to work. My code is below.
{
% Set the overall layout of the tree
\tikzstyle{level 1}=[level distance=3.5cm, sibling distance=3.5cm]
\tikzstyle{level 2}=[level distance=3.5cm, sibling distance=2cm]
% Define styles for bags and leafs
\tikzstyle{bag} = [text width=4em, text centered]
\tikzstyle{end} = [circle, minimum width=3pt,fill, inner sep=0pt]
%TODO: fix top node
\begin{figure}[h]
\centering
\begin{tikzpicture}[grow=right, sloped, scale=0.8]
\node[bag] {$L$}
child {
node[bag] {$D$}
child {
node[bag] {$P$}
child {
node[bag] {$C$}
child {
node[end, label=right:
{$\mathbf{R=1}$}] {}
edge from parent
%node[above] {$E$}
node[below] {$C=0$}
}
child {
node[end, label=right:
{$\mathbf{R=0}$}] {}
edge from parent
%node[above] {$E$}
node[below] {$C=1$}
}
edge from parent
%node[above] {$E$}
node[below] {$P=0$}
}
child {
node[end, label=right:
{$\mathbf{R=0}$}] {}
edge from parent
%node[above] {$E$}
node[below] {$P=1$}
}
edge from parent
%node[above] {$W$}
node[below] {$D=0$}
}
child {
node[end, label=right:
{$\mathbf{R=0}$}] {}
edge from parent
%node[above] {$E$}
node[below] {$D=1$}
}
edge from parent
%node[above] {$W$}
node[below] {$L=0$}
}
child {
child {
node[end, label=right:
{$\mathbf{R=0}$}] {}
edge from parent
%node[above] {$E$}
%node[below] {$C=0$}
}
edge from parent
%node[above] {$B$}
node[below] {$L=1$}
};
\end{tikzpicture}
\end{figure}
}
If anyone who is better at TikZ than I am could help me out with this, it would be greatly appreciated.

R=0node up on level. (Remove one child from the tree.) — 2. Adddraw, circleto thebagstyle. (Which nodes did you mean?) Notes: Should \tikzset or \tikzstyle be used to define TikZ styles?. Also, you might want to look at theforestpackage or the new-ishgraphsandgraphsdrawinglibrary of TikZ for an easier way to create trees.forestpackage, and the results can be seen in my answer. I found that much easier to understand, especially after reading this very helpful answer. – i love fish Apr 29 '15 at 19:10