[Tex/LaTex] Forcing TikZ minimum size for nodes

nodestikz-pgf

I have a tree structure consisting of many unlabelled nodes. However, for some reason the nodes are far larger than I would like and appear to have a minimum size below which the minimum size key is ignored:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{shapes}
\begin{document}
  \begin{tikzpicture}[root/.style={draw,diamond, minimum size=1mm},
                      branch/.style={draw,rectangle},
                      leaf/.style={draw,circle, minimum size=1mm},
                      level 1/.style={sibling distance=5.5em, level distance=1.5em},
                      level 2/.style={sibling distance=2em},
                      level 3/.style={sibling distance=1.5em}]
 \node [root] {}
  child { node[branch] {}
   child { node[leaf] {} }
   child { node[branch] {}
    child { node[leaf] {} }
    child { node[leaf] {} }
   }
  }
  child { node[branch] {}
   child { node[leaf] {} }
   child { node[leaf] {} }
   child { node[leaf] {} }
  }
  child { node[branch] {}
   child { node[branch] {}
    child { node[leaf] {} }
    child { node[leaf] {} }
    child { node[leaf] {} }
   }
   child { node[leaf] {} }
   child { node[leaf] {} }
  }
  child { node[branch] {}
   child { node[leaf] {} }
   child { node[branch] {}
    child { node[leaf] {} }
    child { node[leaf] {} }
   }
   child { node[leaf] {} }
 };
\end{tikzpicture}
\end{document}

Although the minimum size for the root and leaf keys is tiny the nodes are still relatively large.

Best Answer

You also need to adjust inner sep=2pt, depending on how small you want them.

So adjusting your styles as follows:

  \begin{tikzpicture}[root/.style={draw,diamond, minimum size=1mm,inner sep=2pt},
                      branch/.style={draw,rectangle,inner sep=2pt},
                      leaf/.style={draw,circle, minimum size=1mm,inner sep=2pt},
                      level 1/.style={sibling distance=5.5em, level distance=1.5em},
                      level 2/.style={sibling distance=2em},
                      level 3/.style={sibling distance=1.5em}]
  ...

enter image description here