#40 [legend pos] Introduce `legend pos=outer south`

[Jake]

At the moment, there's only one option for placing the legend outside the axis area: legend pos=outer north east. It would be useful to have at least the option outer south available as well, which would place the legend at the bottom of the plot. As explained on the mailling list http://pgfplots-features.706524.n3.nabble.com/Pgfplots-features-legend-pos-outer-td826774.html, this would require checking whether there's an axis label or not, since that would influence the placement.

One way to implement this would be using the following code snippet. It assigns an alias to the x axis label, which then makes it possible to check whether the axis label has been created. If it has, the legend is placed relative to the axis label, if it hasn't, the xticklabel cs is used. See http://tex.stackexchange.com/questions/115490/pgfplots-scale-legend-position-when-below-xlabel for an example

\makeatletter
\pgfplotsset{
    every axis x label/.append style={
        alias=current axis xlabel,
    },
    legend pos/outer south/.style={
        /pgfplots/legend style={
            at={%
                (%
                    \@ifundefined{pgf@sh@ns@current axis xlabel}%
                    {xticklabel cs:0.5}%
                    {current axis xlabel.south}%
                )%
            },
            anchor=north
        },
    },
}
\makeatother

[Stefan Pinnow]

For the record:
I want this feature request + a few more positions which can be found in https://sourceforge.net/p/pgfplots/feature-requests/58/