# Labels on node links in tikz

While @cfr provided an excellent solution to my post here, I have a problem when I insert the code in my main document, though it works fine as a standalone document. It gives me the error: ! Illegal parameter number in definition of \pgfmath@expression, suggesting the error is at \end{forest}. While forest seems to be more convenient for tree-diagrams, I find it very difficult. It will take me time to be able sort out my problem of the forest package. I am therefore reproducing my mwe in tikz, with only the tree-diagram and where I want the labels (as commented out in my code).

\documentclass[12pt]{report}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[inner sep=1.5pt]
\node (10) {z}
child { node {x}
child { node {s}}
child { node {t}}}
child { node {y}
child { node {s}}
child { node {t}}}
;
%    \node      (from z to x) {$\frac{\partial z}{\partial x}$};
%    \node      (from z to y) {$\frac{\partial z}{\partial y}$};
%    \node      (from x to s) {$\frac{\partial x}{\partial s}$};
%    \node      (from x to t) {$\frac{\partial x}{\partial t}$};
%    \node      (from y to s) {$\frac{\partial y}{\partial s}$};
%    \node      (from y to t) {$\frac{\partial y}{\partial t}$};

\end{tikzpicture}
\end{document}


Suggestion only with TikZ:

\documentclass[12pt]{report}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[inner sep=1.5pt]
\node (10) {z}
[ auto,
sibling distance=2.4cm,
level distance=2cm,
level 2/.append style={
sibling distance=1.8cm,
level distance=1.5cm
},
edge from parent/.append style={nodes={pos=.6}}
]
child { node {x}
child { node {s}
edge from parent node[swap]{$\frac{\partial x}{\partial s}$}
}
child { node {t}
edge from parent node{$\frac{\partial x}{\partial t}$}
}
edge from parent node[swap]{$\frac{\partial z}{\partial x}$}
}
child { node {y}
child { node {s}
edge from parent node[swap]{$\frac{\partial y}{\partial s}$}
}
child { node {t}
edge from parent node{$\frac{\partial y}{\partial t}$}
}
edge from parent node{$\frac{\partial z}{\partial y}$}
}
;
\end{tikzpicture}
\end{document}


• Thank you very much @esdd. This works perfectly for me. This, together with forest code from cfr provides me very good learning material. I am very grateful to both of you. Hoping this be your best year ever. – Zilore Mumba May 23 '17 at 15:18