如图所示，怎样把折线图放在柱形图的上面，
ggplot(data=X1026am,aes(x=Group,y=Moisture))+
  stat_summary(geom="bar",fun=mean,aes(fill=Group))+
  stat_summary(geom="errorbar",fun.min=min,fun.max = max,
               width=0.2)+
    scale_fill_manual(values =cols[c(650,173,193,203,213,223,487,488)])+
  stat_summary(data=X1026am,fun = "mean", geom = "point",fill="Green",colour="Green",shape=21,size=3.5)+
  stat_summary(data=X1026am,fun="mean",geom="line",group=1,colour="blue",size=1.2,linetype="dashed")