@Balinus. Thanks. Actually, there is nothing fancy about the plot - just stack of plot layers. The one shown here comprises of 12 layers - six Geom.point and six Geom.line (function)). However, this is an expensive exercise for Gadfly. Luckily the data points are not that too many. The gist of this post is there is an issue with layer ordering for plot with mixed Geom.point and Geom.line, i.e. Geom.line got buried under Geom.point. @Mattriks showed a workaround, while waiting for the bug to be fixed.
The star2 are binning averages, with different color for different averaging method (Arithmetic, Geometric, Harmonic, etc.). The lines are curve fit bin averages.