png( "commits_day.png", width = 1000, height= 700 ) 
print( xyplot( commits ~ date , data = daydata, ylab = "commits / day",
    panel = function(x, y, ...){
        panel.yearlines( )
        panel.abline( h = seq( 0, 50, by = 5), lwd = .5, col = "gray" )
        panel.loess.fill( x, y, lwd = 5, col = "black", ... )
        panel.xyplot( x, y, pch = "+", ... )
    }, ylim = c(0, 30), axis = axis.releases ) )
dev.off()