Contour and surface plot from input data in pgfplots

Question

I have a file of data, data.dat. I am using filecontents to import the data and make plots. Consider the following very small snippet:

n   m   data1    data2
2   2   900.00   981.00 
2   3   600.40   675.00
2   4   450.12   428.01
2   5   360.50   534.98
3   2   225.00   219.80
3   3   150.00   140.00
3   4   112.50   111.00
3   5   90.00    98.00

This is a snippet of the actual length of the data. I would like to make a contour plot of data1 which is easily done using this example from PGFPlots.net. However, similar to this example, I would like to add a projection of the surf plots onto the xz-plane and yz-planes.

Unlike the example, there is not an equation to define the distribution onto these axes. How could this be done? The MWE is shown below. I want to change this to a contour plot similar to this.

MWE

\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\usepgfplotslibrary{colorbrewer}
\usepackage{colorbrewer}
\usepackage{sfmath}
\usepackage{filecontents}           

\begin{document}

\pgfplotsset{
colormap={whitered}{color(0cm)=(white); color(1cm)=(orange!75!red)}}


\pgfplotstableread{StretchingResultsQCRB.dat}{\stretch}
\begin{tikzpicture}
\begin{axis}[width=\columnwidth,
    height=0.618\columnwidth,
    xmin=2,
    xlabel={$x$},
    ylabel={$y$},
    zlabel={$P(x,y)$},
    xlabel style = {font=\Large, yshift=1ex},
    ylabel style = {font=\Large, yshift=1ex},
    zlabel style = {font=\Large, yshift=-1ex},  
    zmode=log,  
    ymin=1,
    view={20}{50},
    axis line style={line width=1pt},
    colormap name=whitered,
    colorbar,
        colorbar style={
                at={(1,0)},
                anchor=south west,
                height=0.25*\pgfkeysvalueof{/pgfplots/parent axis height},
                %title={$P(x_1,x_2)$}
    }
]
    \addplot3[surf, line width=0.8pt] table [x={n}, y={m}, z={QCRBa0.5}] {\stretch};
\end{axis}
\end{tikzpicture} 


\end{document}