Set axis x line to other origin than 0

I am trying to make a ybar axis that averages from the middle, but I cannot find a way to change the origin of the x axis.

This is what I want:

This is what I have:

As you can see, I am trying to make an average. Can I do it like this or do I have to transform my data?

\documentclass{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}

\begin{axis}[ybar,
xticklabels from table={\datatable}{variable},
xtick=data,
axis x line=middle,
ymin=1,
ymax=5
]

\end{axis}
\end{tikzpicture}
\end{document}

-
I'm not sure what you mean by "trying to make an average" / "averages from the middle". From the screenshot, it looks like you just want the bars to start from y=3, instead of y=0, right? Is 3 the average of something? – Jake Jun 16 '12 at 14:06
Yes exactly that. Participants rate questions on a scale from 1 to 5. So the question is indeed: How do I start the x axis on y=3? – Marnix Jun 16 '12 at 14:11

ybar plots always start from y=0. So what you'll have to do is change the tick labels on the y axis, so that 0 "looks like" 3, and subtract 3 from the data values, which you can do using a y filter/.code.

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
X averagejs averagem variable
1 3.5 3.7 A
2 4 4.4 B
3 3.6 3.9 C
}\datatable

\begin{axis}[ybar,
xticklabels from table={\datatable}{variable},
xtick=data,
axis x line*=middle,
enlarge x limits,
y filter/.code={\pgfmathparse{#1-3}},
ymin=-2, ymax=2,
yticklabel={\pgfmathparse{\tick+3}\pgfmathprintnumber{\pgfmathresult}}
]