Dear R-help , Here I try to explain the problem setting problem setting: we have four variables
y: outcome x:exposure u:confounder z:Instrumental Variable ##we have instrumental variable as distance between centers and patients place, we have many ##centers for exp:three centers c1,c1,c3 and of course n patients. we aim to find out what would happen if a well defined group of patients were treated by provider c1 or c2 rather than provider B. ##Instrumental Variable: distance centers and patients ##i:number of patients ##If we have 3 centers c1,c2,c3 ##d1:distance between center c1 and patient (i) ##d2:distance between center c2 and patient (i) ##d3:distance between center c3 and patient (i) ##To generate distance d1,d2,d3 and choice nearest center n<-10 wcoord<-runif(n, min=0, max=1) hcoord<-runif(n, min=0, max=1) ## (w1,h1),(w2,h2),(w3,h3) position of the 3 centers w1<-0.9 h1<-0.3 w2<-0.2 h2<-0.6 w3<-0.7 h3<-0.1 d1<-sqrt((wcoord-w1)^2 +(hcoord-h1)^2) d2<-sqrt((wcoord-w2)^2 +(hcoord-h2)^2) d3<-sqrt((wcoord-w3)^2 +(hcoord-h3)^2) ##m:nearest center to patient m<-pmin(d1,d2,d3) z<-cbind(d1,d2,d3,m) d1 d2 d3 m [1,] 0.87142373 0.2750814 0.89725053 0.27508142 [2,] 0.64285521 0.5237454 0.78950397 0.52374540 [3,] 0.06799528 0.7101305 0.30996833 0.06799528 [4,] 0.41636986 0.7966441 0.67216852 0.41636986 [5,] 0.29930080 0.7204538 0.02085061 0.02085061 ###Instrumental Variable as relative distance R1 R2 R3 R1<-(d1/sum(m)) R2<-(d2/sum(m)) R3<-(d3/sum(m)) z<-cbind(d1,d2,d3,m,R1,R2,R3) z d1 d2 d3 m R1 R2 [1,] 0.47371700 0.4791628 0.2733683 0.27336832 0.17374723 0.17574461 [2,] 0.04784215 0.7305729 0.2384407 0.04784215 0.01754727 0.26795537 [3,] 0.06238730 0.8167800 0.2820744 0.06238730 0.02288206 0.29957393 R3 [1,] 0.10026448 [2,] 0.08745394 [3,] 0.10345767 ##generate confounders as : u<-rnorm(n,0,1) C:center choice I think we can use multinomial model as rmultinom(n, size, prob). I want to generate the data like that i d1 d2 d3 m R1 R2 R3 P1 P2 P3 C U Y1 Y2 Y3 Yi any one have text or notes about that? Yours Sincerely, Tamer -- View this message in context: http://r.789695.n4.nabble.com/instrumental-variable-as-distance-tp3381900p3381900.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list 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.