# Only one xlabel for matrix of plots in pgfplots

I am looking for a way to make only one xlabel for a matrix of plots with pgfplots. My current plot looks like this

and would like a xlabel where the red circle is drawn.

The code for the plot is quite long, but here goes.

\begin{figure}[ht]
\centerfloat
% The VCG

\subbottom[VCG with no rotation. QRS-axis angle: 30 degrees]{\label{fig:0rotationFrontalVCG}%
$\vcenter{\hbox{ \begin{tikzpicture} \begin{axis}[ title = {Frontal VCG}, axis equal image, xlabel= {Right to Left}, ylabel= {Inferior to Superior}, ymin = -1000, ymax = 1000, xmin = -1000, xmax = 1000, ] % Plot the VCG \addplot[black] table[x = VCGX, y expr = \thisrow{VCGY}*(-1), select coords between index={239}{282}] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat} [postaction={decorate, decoration={markings, mark=between positions 1/15 and 1 step 1/15 with {\arrow[black,line width=1.5pt]{>};} }}] ; % Add the circle \draw (axis cs:0,0) circle [black, radius=892.1472]; % Add the axis through (0,0) \addplot[black, -] coordinates {(0, -895) (0, 895)}; \addplot[black, -] coordinates {(-895, 0) (895, 0)}; % Add the QRS-axis \addplot[red, ->, -triangle 60, line width = 1pt] coordinates {(0, 0) ({cos(-30)*895}, {sin(-30)*895})}; \end{axis} \end{tikzpicture} }}$
}
% The 6 ECG's
$\vcenter{\hbox{ \begin{tikzpicture} \pgfplotsset{small} \matrix { \begin{axis}[title = Lead aVL, width=0.4\textwidth] \addplot[black] table[x expr=\coordindex, y=aVL] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \pgfmatrixnextcell \begin{axis}[title = Lead II, width=0.4\textwidth] \addplot[black] table[x expr=\coordindex, y=II] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \\ \begin{axis}[title = Lead I, width=0.4\textwidth,ylabel=Amplitude]] \addplot[black] table[x expr=\coordindex, y=I] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \pgfmatrixnextcell \begin{axis}[title = Lead aVF, width=0.4\textwidth] \addplot[black] table[x expr=\coordindex, y=aVF] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \\ \begin{axis}[title = Lead -aVR, width=0.4\textwidth] \addplot[black] table[x expr=\coordindex, y expr = \thisrow{aVR}*(-1)] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \pgfmatrixnextcell \begin{axis}[title = Lead III, width=0.4\textwidth] \addplot[black] table[x expr=\coordindex, y=III] {data/vcg_analysis_section/frontal_vcg_rotation/30degree.dat}; \end{axis} \\ }; \end{tikzpicture} }}$
}

\caption{Caption for the whole figure}
\label{fig:}
\end{figure}


The label should be placed in the middel of the two last plots.

• I'm sure you would like using groupplots library of pgfplots. – percusse Dec 1 '14 at 23:09
• Thank you @percusse that help me a lot to clean up the code and eventually finding the answer – Kasper Sørensen Dec 2 '14 at 10:30