[R] Weighted Average application on Summary Dataset

[RaoulD]

Hi,

I have 2 huge datasets - May and Jun - a miniscule sample of one is given
below. I am trying to do 2 things with these datasets. I need to verify if
the weighted average of variable A for a Reason in Jun is same/different
from the same for May. To do this I am first computing the weighted average
for each SubReason using a function I wrote. 

Where I need help is applying the function on both the datasets to arrive at
weighted averages for each SubReason. Then, I would like to know what the
best way would be, to compare the weighted average for a sub reason across 2
datasets to be able to state that there is a difference - t-test,ANOVA?
Would greatly appreciate any help!! The function I wrote for weighted
average computation is given below the dataset.

One of the datasets:

Reason	SubReason    A	N
A	           SR1	      1115	29
B	           SR2	      734	24
B	           SR2	      1054	31
A	           Sr1	              600	43
A	           SR3	      1033	60
A	           Sr1	              1163	30
B	           SR4	      732	43
B	           SR4	      988	70
A	           SR3	      569	25
B	           SR4	      1073	65

Output I require:
R	SR	WA_A	                   N (Sum of N)
A	SR1	   912.0098	             102
	SR3	   896.5294118	     85
B	SR2	   914.3636364	     55
	SR4	   957.1966292	     178
		(Weighted Average 
                of A for N weights)

# FUNCTION TO CALCULATE THE WEIGHTED AVERAGE FOR A WEIGHTED BY N       
WA<-function(A,N) {
         sp_A<-c(A %*% N)
         sum_N<-sum(N)
         WA<-sp_A/sum_N   
         return(WA)      
         }

Thanks in advance!
Raoul




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