# How to set style of a single edge in the tree (TikZ) ?

The Tikz manual gives "edge from parent" construct.
But it is peculiar (it changes all the edges in subtree and some nodes).
How to color and thicken exactly one edge?

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As Mikael mentioned in his answer to your previous question, I don't think this is actually a bug, but simply how TikZ works. So the solution to the problem is to change a specific branch, and then change it back on its daughters. As you ask in your comment, you can define two styles for plain and emphasized edges respectively, to save you some typing:

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture} [
level 1/.style={sibling distance = 2cm, level distance = 1cm},
level 2/.style={sibling distance = 1cm},
level 3/.style={sibling distance = 1cm},
every node/.style={circle, draw=black,thin, minimum size = 0.5cm},
emph/.style={edge from parent/.style={red,very thick,draw}},
norm/.style={edge from parent/.style={black,thin,draw}}
]

\begin{scope}[xshift=6cm]
\node{}
child[emph] { node {}
child[norm] { node {} }
child[norm] { node {}
child[emph] { node {} }
child { node {} }
}
}
child { node {}
child { node {} }
child { node {} }
}
child { node {} }
;
\end{scope}
\end{tikzpicture}

\end{document}

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Can I save a whole style to a variable and use it like that: child[SAVED_STYLE] ? –  Łukasz Lew Jan 18 '11 at 19:59
Yes. I've updated my answer to reflect that. –  Alan Munn Jan 18 '11 at 20:13
Can I replace: "emph/.style={edge from parent/.style={red,very thick,draw}}" with "emph/.style={red,very thick,draw}" ? –  Łukasz Lew Jan 18 '11 at 22:07
@Lukasz Why not try it and experiment? (You can't, though.) –  Alan Munn Jan 18 '11 at 22:25
I did, it worked, that's why I asked :) –  Łukasz Lew Jan 20 '11 at 4:10
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