The ability to automatically equalize the marker size of the legend and plot markers when using the SCATTER function is not available in MATLAB 7.9 (R2009b).
You may use either of the following workarounds to create a scatter plot in which the legend markers have the same size as the plot markers:
1. Manually set the marker size of the patch objects in the legend. Note that the marker area input to the SCATTER function is specified in square points, whereas the 'MarkerSize' property of a patch object is given in points:
M = findobj(h,'type','patch')
Note that this workaround only applies to releases R2014a and prior. The legend graphics object hierarchy changed in R2014b.
2. Use the PLOT function instead of the SCATTER function:
figure; hold on
plot(1,1,'ko', 'MarkerSize', 12)
plot(1,2,'k+', 'MarkerSize', 12)
plot(2,1,'kx', 'MarkerSize', 12)
h = legend('Circle', 'Plus', 'X', 'Location', 'NorthEast');
set(h, 'FontSize', 14)
axis([0 3 0 3])