thank you very much Jim! I'll try it. bw c Sent from my iPhone
> Em 30/06/2016, às 20:33, Jim Lemon <drjimle...@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.m...@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]] >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.