Plot non-continuous function with TikZ

Question

How can I plot a non-continuous function with TikZ (using continuous lines for continous stretches of the function and dashed lines for discontinuities)? Does anybody know an efficient method?

Answer 1

I am not sure if this is what you want, but I would suggest you to use the pgfplots package (internally uses TikZ); a little example (the solid and hollow dot styles are borrowed from a comment by cmhughes):

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.6}

\pgfplotsset{soldot/.style={color=blue,only marks,mark=*}} \pgfplotsset{holdot/.style={color=blue,fill=white,only marks,mark=*}}

\begin{document}

\begin{tikzpicture}
\begin{axis}
\addplot[domain=0:4,blue] {x*x};
\addplot[domain=4:6,blue] {x};
\addplot[domain=6:10,blue] {-5};
\draw[dotted] (axis cs:4,16) -- (axis cs:4,4);
\draw[dotted] (axis cs:6,6) -- (axis cs:6,-5);
\addplot[holdot] coordinates{(0,0)(4,4)(6,-5)};
\addplot[soldot] coordinates{(4,16)(6,6)(10,-5)};
\end{axis}
\end{tikzpicture}

\end{document}