[R] Command to combine means?

[Carlos Renato M. Maia]

thank you very much Jim!
I'll try it.
bw
c

Sent from my iPhone

> Em 30/06/2016, às 20:33, Jim Lemon <drjimlemon at gmail.com> escreveu:
> 
> Hi Carlos,
> The STATA function assumes estimated population SDs. If you have
> sample SDs you can specify with this:
> 
> combine<-function(n,mu,sd,sd.type=c("pop","sample")) {
> N<-sum(n)
> mean<-sum(n*mu)/N
> if(sd.type[1]=="sample") {
>  meanss<-(n[1]*(mean-mu[1])^2+n[2]*(mean-mu[2])^2)/N
>  SD<-sqrt(sum(sd*sd*n)/N+meanss)
> } else {
>  meanss<-(n[1]*(mean-mu[1])^2+n[2]*(mean-mu[2])^2)/(N-1)
>  SD<-sqrt(sum(sd*sd*(n-1))/(N-1)+meanss)
> }
> return(list(N,mean,SD))
> }
> combine(c(12,34),c(3,45),c(1,4))
> combine(c(12,34),c(3,45),c(1,4),"sample")
> 
> Jim
> 
> 
> On Fri, Jul 1, 2016 at 1:02 AM, Carlos R. Moreira Maia
> <crm.maia at gmail.com> wrote:
>> Dear all,
>> I'm newbie with R (changing from STATA), and I can't find some commands.
>> One of those is the "combine", which I use to combine means like this:
>> 
>> --------------------------------------------
>> n1 m1 sd1  n2 m2 sd2
>> 
>> combine 12 3 1 34 45 4
>> 
>> Combine has calculated the following values:
>>    combined n = 46
>>    combined mean = 34.043478
>>    combined SD = 18.964829
>> --------------------------------------------
>> 
>> Does anybody knows a simmilar command in R to combine means?
>> 
>> Thanks in advance.
>> 
>> Carlos.
>> 
>>        [[alternative HTML version deleted]]
>> 
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