Collapsing a factor in R

I'm trying to collapse the following table along the sub-group factor.  In
this case, collapsing means taking the average ages within a subgroup and
creating a new table.  I seem to be running into trouble trying to create
this new data frame. I can use the ave() function to find averages within a
subgroup but how do I maintain the Group/Gender factors after collapsing?
(see bottom table) Can anyone help??

Thanks in advance!!

Here's the starting point (table)

Age   Group  SubGroup	Gender
12	g1	a	f
32	g1	a	f
81	g1	a	f
63	g1	b	m
24	g1	b	m
24	g1	b	m
70	g1	c	f
82	g1	c	f
71	g1	c	f
61	g1	c	f
25	g2	d	m
29	g2	d	m
43	g2	e	f
17	g2	e	f
42	g2	e	f
55	g2	e	f
52	g2	f	f
19	g2	f	f
12	g2	f	f

The following is what I'm trying to achieve (as a new dataframe)

AvgAgeSubgroup	Group	Subgroup	Gender
41.67			g1	a		f
37			g1	b		m
71			g1	c		f
27			g2	d		m
39.25			g2	e		f
27.67			g2	f		f

Can anyone help?

-Scott




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