[R] Averaging within a range of values

[doggysaywhat]

Hello all.

I have two data frames.  
Group       Start          End
G1	               200	         700
G2	               500	         1000
G3	               2000        3000
G4	               4000        6000
G5	               7000        8000


and

Pos		    C0		    C1
200		    0.9	  	  0.6
500	   	  0.8	   	  0.8
800		    0.9	  	  0.7
1000		  0.7	  	0.6
2000	  	0.6		  0.4
2500	  	1.2	  	0.8
3000	  	0.6	  	1.5
3500	  	0.7	  	0.7
4000	  	0.8		  0.8
4500	  	0.6	  	0.6
5000		  0.9	  	0.9
5500	  	0.7		  0.8
6000	  	0.8	  	0.7
6500	  	0.4	  	0.4
7000		  0.5	  	0.8
7500  		0.7		  0.9
8000	  	0.9	  	0.5
8500	  	0.8	  	0.6
9000	  	0.9	  	0.8


I need to conditionally average all values in columns C0 and C1 based upon
the bins I defined in the first data frame.  For example, for the bin G1 in
the first dataframe, the values are 200 to 700 so i would average the value
at pos 200 (0.9) and 500 (0.8) for C0 and then perform the same thing for
C1.  

I can do this in excel with array formulas but I'm relatively new to R and
would like know if there is a function that will perform the same action.  I
don't know if this will help, but the excel array function I used was
average(if(range>=start)*(range<=end),range)).  Where the range is the
entire pos column.  

Initially I looked at the aggregate function.   I can use aggregate when I
give a single vector to be used for grouping such as (A,B,C) but I'm not
sure how to define grouping as the bin 200-500 and the second bin as
500-1000 etc. and use that as my grouping vector.   

Any help would be greatly appreciated.  


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