Possible Duplicate:
pgfplots: externalization and legend referencing
I am trying to implement references to plots using there legend image with pgfplots.
I use the example on page 164 of the manual:
\documentclass{article}
% This part of preamble works
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\pgfplotsset{width=7cm,compat=newest}
% This part of preamble generates an error (see below)
\usetikzlibrary{external}
\tikzexternalize[prefix=tikz/,shell escape=-enable-write18]
\begin{document}
\begin{tikzpicture}[baseline]
\begin{axis}
\addplot+[only marks,
samples=15,
error bars/y dir=both,
error bars/y fixed=2.5]
{3*x+2.5*rand};
\label{pgfplots:label1}
\addplot+[mark=none] {3*x};
\label{pgfplots:label2}
\addplot {4*cos(deg(x))};
\label{pgfplots:label3}
\end{axis}
\end{tikzpicture}
The picture shows the estimations \ref{pgfplots:label1} which are subjected to noise.
It appears the model \ref{pgfplots:label2} fits the data appropriately.
Finally, \ref{pgfplots:label3} is only here to get three examples.
\end{document}
When I want to use externalization, the second block of the preamble generates an error or simply non working references (??, on a more complicated example).
The error message is not explicit but I noticed this in the log file:
! Undefined control sequence.
l.1 ...[/pgfplots/every crossref picture]\pgfplots
@draw@image
l.32 blablabla \ref{pgfplots:label1}
Do you know what I am doing wrong?
