I have a data frame Df_agg:
    Planned.start.date  Parent.Application.Release  Actual.Hours    Estimated.Effort
1   7/16/14             REL0000801                  0               1
2   8/20/14             REL0000802                  4               11
3   9/17/14             REL0000805                  31              21
4   10/15/14            REL0000808                  102             74
5   11/19/14            REL0000809                  78              80
6   12/17/14            REL0000812                  133             73
7   1/22/15             REL0002534                  12              11
I plot a barplot using ggplot
ggplot(Df_agg, aes(x=interaction(Planned.start.date,Parent.Application.Release), y=Actual.Hours))+ geom_bar(stat="identity") + 
  labs(x="Release", y="Hours")
and get this
I do the same thing but to plot Estimated effort this time
ggplot(Df_agg, aes(x=interaction(Planned.start.date,Parent.Application.Release), y=Estimated.Effort))+ geom_bar(stat="identity") + 
  labs(x="Release", y="Estimated Effort")

What I want to do is to merge these two plots into one , since the y value of both are numeric this should be possible by concept .
My ideal Graph would be some thing like this :

PS: I have created the last graph using my messy image editing skills so its purpose is just to get the want I am looking for ,sorry if its not perfect
