Grouped bar chart

% Source: http://tex.stackexchange.com/a/69234/5645
\documentclass[varwidth=true, border=2pt]{standalone}

\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary{arrows, positioning, calc}

\begin{document}
    \newcommand\shift{1.5}

    \begin{tikzpicture}[scale=1]
        \begin{axis}[
            ybar,
            ylabel={vaule},
            ylabel style={at={(0.02,0.5)}, color=red},
            xlabel={items},
            legend style={at={(0.5,-0.15)},
            anchor=north,legend columns=-1},
            width=0.8*\textwidth,
            height=9cm,
            bar width=7pt,
            symbolic x coords={
                $x_1$,$x_2$,$x_3$,$x_4$,$x_5$,$x_6$, $x_7$, $x_8$,
                $x_9$, $x_{10}$, $x_{11}$, $x_{12}$, $x_{13}$,
                $x_{14}$, $x_{15}$
            },
            xtick=data,
            scaled y ticks=base 10:-3,
            axis y line*=left,
            %nodes near coords,
            %nodes near coords align={vertical},
        ]
            \addplot[red, fill=red!15, shift={(-\shift,0)}] coordinates {
                ($x_1$,96000) ($x_2$,126000) ($x_3$,115000)
                ($x_4$,125000) ($x_5$,123000) ($x_6$, 123000)
                ($x_7$, 112000) ($x_8$, 111000) ($x_9$, 110000)
                ($x_{10}$, 110000) ($x_{11}$, 120000)
                ($x_{12}$, 98000) ($x_{13}$, 130000)
                ($x_{14}$, 87000) ($x_{15}$, 97000)};
        \end{axis}
        \begin{axis}[
            ybar,
            ylabel={weight},
            ylabel style={at={(1.25,0.5)}, color=blue},
            legend style={at={(0.7,-0.15)},
            anchor=north,legend columns=-1},
            width=0.8*\textwidth,
            height=9cm,
            bar width=7pt,
            symbolic x coords={
                $x_1$,$x_2$,$x_3$,$x_4$,$x_5$,$x_6$, $x_7$, $x_8$,
                $x_9$, $x_{10}$, $x_{11}$, $x_{12}$, $x_{13}$,
                $x_{14}$, $x_{15}$
            },
            xtick=data,
            %nodes near coords,
            %nodes near coords align={vertical},
            axis y line*=right,
            axis x line=none,
        ]
            \addplot +[shift={(\shift,0)}] coordinates {($x_1$,27)
                ($x_2$,21) ($x_3$,27)  ($x_4$,15) ($x_5$,19)
                ($x_6$, 46) ($x_7$, 47) ($x_8$, 32) ($x_9$, 14)
                ($x_{10}$, 20) ($x_{11}$, 50) ($x_{12}$, 19)
                ($x_{13}$, 22) ($x_{14}$, 50) ($x_{15}$, 46)};
        \end{axis}
    \end{tikzpicture}
\end{document}