Bar Chart Patterns in Legend

Question

I have a groupplot with three bar charts using a common legend. This worked great when I was using color, but now I have to prep for publication in black and white. I'm not well versed at all in pgfplots.

I changed the bars from solid color fills to patterns, but I don't know how to produce a useful legend now. Any help on how I could get the patterns into the legend is most appreciated.

    \documentclass{article}

    \usepackage{pgfplots}
    \usetikzlibrary{patterns}

    \begin{document}

    \begin{figure}
        \centering
        \begin{tikzpicture}
            \begin{groupplot}[
                    legend columns=-1,
                    legend entries={{\color{red}{\tiny Random}},{\color{blue}{\tiny ++Cost}},{\color{black}{\tiny ++FTE}},{\color{green}{\tiny ++Resources}},{\color{orange}{\tiny Hold All}}},
                    legend to name=CombinedLegendBar,
                    footnotesize,
                    group style={
                    group size=3 by 1,
                    xlabels at=edge bottom,
                    ylabels at=edge left,
                    xticklabels at=edge bottom}]
                \nextgroupplot[title={\scriptsize Empirical CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {  (1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates { (2, 8.501)};
                    \addplot[ybar, pattern=grid] coordinates {  (3, 10.179)};
                    \addplot[ybar, pattern=dots] coordinates {  (4, 11.14)};
                    \addplot[ybar, pattern=north east lines] coordinates {  (5, 15.001)};

                \nextgroupplot[title={\scriptsize Triangular CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {(1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates {(2, 7.745)};
                    \addplot[ybar, pattern=grid] coordinates {(3, 8.606)};
                    \addplot[ybar, pattern=dots] coordinates {(4, 8.630)};
                    \addplot[ybar, pattern=north east lines] coordinates {(5, 15.001)};

                \nextgroupplot[title={\scriptsize LN/Exponential CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {  (1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates {    (2, 8.428)};
                    \addplot[ybar, pattern=grid] coordinates {  (3, 9.964)};
                    \addplot[ybar, pattern=dots] coordinates {  (4, 11.087)};
                    \addplot[ybar, pattern=north east lines] coordinates {  (5, 15.001)};

            \end{groupplot}
        \end{tikzpicture}
        \ref{CombinedLegendBar}
        \caption{Triage++ Performance}
        \label{PlusPlusCombinedBar}
    \end{figure}
\end{document}

Answer 1

You can add the option ybar legend explained in page 211 of the v1.12 manual to the axis options. You can also use the area legend option in the axis options, explained on the same page of the manual. Note that I had to load the groupplots library and set the compatibility compat=1.12 in your MWE.

\documentclass{article}

    \usepackage{pgfplots}
    \usepgfplotslibrary{groupplots}
    \pgfplotsset{compat=1.12}
    \usetikzlibrary{patterns}

    \begin{document}

    \begin{figure}
        \centering
        \begin{tikzpicture}
            \begin{groupplot}[
                    legend columns=-1,
                    legend entries={{\color{red}{\tiny Random}},{\color{blue}{\tiny ++Cost}},{\color{black}{\tiny ++FTE}},{\color{green}{\tiny ++Resources}},{\color{orange}{\tiny Hold All}}},
                    legend to name=CombinedLegendBar,
                    footnotesize,
                    ybar legend,
                    % area legend, % This is the alternate option
                    group style={
                    group size=3 by 1,
                    xlabels at=edge bottom,
                    ylabels at=edge left,
                    xticklabels at=edge bottom}]
                \nextgroupplot[title={\scriptsize Empirical CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {  (1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates { (2, 8.501)};
                    \addplot[ybar, pattern=grid] coordinates {  (3, 10.179)};
                    \addplot[ybar, pattern=dots] coordinates {  (4, 11.14)};
                    \addplot[ybar, pattern=north east lines] coordinates {  (5, 15.001)};

                \nextgroupplot[title={\scriptsize Triangular CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {(1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates {(2, 7.745)};
                    \addplot[ybar, pattern=grid] coordinates {(3, 8.606)};
                    \addplot[ybar, pattern=dots] coordinates {(4, 8.630)};
                    \addplot[ybar, pattern=north east lines] coordinates {(5, 15.001)};

                \nextgroupplot[title={\scriptsize LN/Exponential CDF}, xticklabels=\empty]
                    \addplot[ybar, pattern=horizontal lines] coordinates {  (1, 6.886)};
                    \addplot[ybar, pattern=vertical lines] coordinates {    (2, 8.428)};
                    \addplot[ybar, pattern=grid] coordinates {  (3, 9.964)};
                    \addplot[ybar, pattern=dots] coordinates {  (4, 11.087)};
                    \addplot[ybar, pattern=north east lines] coordinates {  (5, 15.001)};

            \end{groupplot}
        \end{tikzpicture}
        \ref{CombinedLegendBar}
        \caption{Triage++ Performance}
        \label{PlusPlusCombinedBar}
    \end{figure}
\end{document}

ybar legend:

area legend: