# Fill square mark in legend?

I'm using the following code to generate a simple graph, and I want to have the legend show a filled in gray square to represent the shaded area on the graph. Everything still leads to a white square mark.

\begin{tikzpicture}
\begin{axis}[
inner axis line style={>={Latex[round]}},
axis lines=left,
ymin=0,
ymax=10,
xmin=0,
xmax=10,
yticklabels={,,},
xticklabels={,,},
ticks=none,
xlabel=Quantity (q),
ylabel=Price (\$), legend entries={ total willingness to pay, marginal willingness to pay }, legend pos=north east, legend style={draw=none} ] \addlegendimage{only marks, mark=square} \addlegendimage{only marks, mark=o} \addplot[solid,domain=0:10,samples=100]{-5/2*x^(1/2)+15/2}; \addplot[draw=none,name path=A,domain=3:6,fill=gray]{-5/2*x^(1/2)+15/2}\closedcycle; \end{axis} \end{tikzpicture} Thank you for your help! • @Jake, oh, with that short answer you were way quicker than I was ;) – Stefan Pinnow Feb 18 '16 at 16:05 • @Jake Thank you both so much for your help! That simple fix was taking so much time to figure out on my own – Zachary Grzelka Feb 18 '16 at 16:09 ## 1 Answer You have to use mark=square* instead of mark=square to fill it. With color you can than fill it with a color of your choice. \documentclass[border=1mm]{standalone} \usepackage{pgfplots} \begin{document} \begin{tikzpicture} \begin{axis}[ inner axis line style={>={Latex[round]}}, axis lines=left, ymin=0, ymax=10, xmin=0, xmax=10, yticklabels={,,}, xticklabels={,,}, ticks=none, xlabel=Quantity (q), ylabel=Price (\$),
legend entries={
total willingness to pay,
marginal willingness to pay
},
legend pos=north east,
legend style={draw=none}
]