R: [R] weighted.mean and tapply (again)

[Guazzetti Stefano]

what about using "mapply"?

 splitted.value<-with(x.1, split(VALUE, GROUP))
 splitted.freq<-with(x.1, split(FREQUENCY, GROUP))
 mapply(weighted.mean, splitted.value, w=splitted.freq)


Stefano


   >-----Messaggio originale-----
   >Da: r-help-bounces at stat.math.ethz.ch
   >[mailto:r-help-bounces at stat.math.ethz.ch]Per conto di
   >james.holtman at convergys.com
   >Inviato: mercoledì 25 maggio 2005 17.57
   >A: Dan Bolser
   >Cc: R mailing list; r-help-bounces at stat.math.ethz.ch
   >Oggetto: Re: [R] weighted.mean and tapply (again)
   >
   >
   >
   >
   >
   >
   >> x.1 <- read.table('clipboard',header=T)
   >> x.1
   >   GROUP VALUE FREQUENCY
   >1      2     2        78
   >2      2     3        40
   >3      2     4        16
   >4      2     5         3
   >5      2     6         1
   >6      2     8         1
   >7      3     3        19
   >8      3     4        10
   >9      3     5        19
   >10     3     6         4
   >> by(x.1, x.1$GROUP, function(x) weighted.mean(x$VALUE, 
   >x$FREQUENCY))
   >x.1$GROUP: 2
   >[1] 2.654676
   >------------------------------------------------------------
   >---------------
   >x.1$GROUP: 3
   >[1] 4.153846
   >>
   >
   >Jim
   >__________________________________________________________
   >James Holtman        "What is the problem you are trying to solve?"
   >Executive Technical Consultant  --  Office of Technology, Convergys
   >james.holtman at convergys.com
   >+1 (513) 723-2929
   >
   >
   >                                                            
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   >                   
   >                      Dan Bolser                            
   >                                                            
   >                   
   >                      <dmb at mrc-dunn.cam.ac.        To:      
   > R mailing list <r-help at stat.math.ethz.ch>                  
   >                   
   >                      uk>                          cc:      
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   >                      Sent by:                     Subject: 
   > [R] weighted.mean and tapply (again)                       
   >                   
   >                      r-help-bounces at stat.m                 
   >                                                            
   >                   
   >                      ath.ethz.ch                           
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   >                      05/25/2005 11:33                      
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   >
   >
   >I read answers to questions including the words "tapply" and
   >"weighted.mean", but I didn't understand either the problem 
   >(data) or the
   >solution provided.
   >
   >Here is my question ...
   >
   >> dat[1:10,]
   >  GROUP  VALUE FREQUENCY
   >1     2      2        78
   >2     2      3        40
   >3     2      4        16
   >4     2      5         3
   >5     2      6         1
   >6     2      8         1
   >7     3      3        19
   >8     3      4        10
   >9     3      5        19
   >1     3      6         4
   >
   >
   >For each GROUP, I would like to calculate the weighted.mean 
   >of VALUE using
   >the FREQUENCY as the weight, so for the snippet of data 
   >shown that would
   >be...
   >
   >group.2 <- weighted.mean(c(2,3,4,5,6,8),c(78,40,16,3,1,1))
   >group.3 <- weighted.mean(c(3,4,5,6),    c(19,10,19,4))
   >
   >> cbind(rbind(2,3),rbind(group.2,group.3))
   >        [,1]     [,2]
   >group.2    2 2.654676
   >group.3    3 4.153846
   >
   >I would like to use tapply to automatically do this across the whole
   >dataset (dat) - which includes lots of other distinct 
   >grouping factors,
   >however, like I said, I couldn't understand (and therefore 
   >apply to my
   >data) any of the other solutions I found, so any help here would be
   >greatly appreciated!
   >
   >All the best,
   >Dan.
   >
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