TikZ failing to draw [closed]

Question

I'm trying to use TikZ to make flow charts in my LaTeX files, but I'm getting an error. Here's the LaTeX I'm using:

\documentclass[11pt]{article}
\usepackage{tikz}

\begin{document}
Some text
\tikzstyle{decision} = [diamond, draw, fill=blue!20, text width=4.5em, text badly centered, node distance=2.5cm, inner sep=0pt]
\tikzstyle{block} = [rectangle, draw, fill=blue!20, text width=5em, text centered, rounded corners, minimum height=4em]
\tikzstyle{line} = [draw, very thick, color=black!50, -latex']
\tikzstyle{cloud} = [draw, ellipse,fill=red!20, node distance=2.5cm, minimum height=2em]

\begin{tikzpicture}[scale = 2, node distance = 2cm, auto]
\node [block] (init) {initialize model};
\node [cloud, left of=init] (expert) {expert};
\node [cloud, right of=init] (system) {system};
\node [block, below of=init] (identify) {identify candidate models};
\node [block, below of=identify] (evaluate) {evaluate candidate models};
\node [block, left of=evaluate, node distance=3cm] (update) {update model};
\node [decision, below of=evaluate] (decide) {is best candidate better?};
\node [block, below of=decide, node distance=3cm] (stop) {stop};
\end{tikzpicture}

\end{document}

I literally copied-and-pasted this code from an example document, just to use as a test. And here's the error it produces:

Package pgfkeys Error: I do not know the key '/tikz/ellipse' and I am going to ignore it. Perhaps you misspelled it.

Well, I didn't misspell it. I get a similar error message for the diamond as well. How can I fix this?

Thanks a ton!

Answer 1

You should have worked more carefully. You have forgotten to include the tikZ libraries.

\usetikzlibrary{shapes,arrows}

It would have been easier to download the source file instead of copy&paste.