Hi there, data1<-matrix(data=c(1,1.2,1.3,"3/23/2004",1,1.5,2.3,"3/22/2004",2,0.2,3.3,"4/23/2004",3,1.5,1.3,"5/22/2004"),nrow=4,ncol=4,byrow=TRUE) data1<-data.frame(data1) names(data1)<-c("areaid","x","y","date") data1
areaid x y date 1 1 1.2 1.3 3/23/2004 2 1 1.5 2.3 3/22/2004 3 2 0.2 3.3 4/23/2004 4 3 1.5 1.3 5/22/2004 data2<-matrix(data=c(1,1.22,1.32,1, 1.53, 2.34,1, 1.21, 1.37,1, 1.52, 2.35,2, 0.21, 3.33,2, 0.23, 3.35,3, 1.57, 1.31,3, 1.59, 1.33),nrow=8,ncol=3,byrow=TRUE) data2<-data.frame(data2) names(data2)<-c("areaid","x1","y1") data2 areaid x1 y1 1 1 1.22 1.32 2 1 1.53 2.34 3 1 1.21 1.37 4 1 1.52 2.35 5 2 0.21 3.33 6 2 0.23 3.35 7 3 1.57 1.31 8 3 1.59 1.33 Explains the two data. You can treat data1 as case dataset and data2 as control dataset,respectively.Note th number of recodes for data2 are 2 times as that of data1 for each records,something like 1:2 matched case-control study design. I hope to merge data1 and data2. Take areaid=1 as an example. >From the two dataset, we can see that data1 has two points(x,y) in areaid=1, and data2 has four points (x1,y1) in areaid=1. Each record in data1 will have two matched records in data2.I want to randomly select 1/2 points of areaid=1 in data2 to link the one record of areaid=1 in the data1, and the other 1/2 points of areaid=1 in data2 to link the other record of areaid=1 in the data1.Actually,the number of records in the same areaid will be over 2 in the actual dataset. This is only an example to explain the problem. For the cases of areaid=2 or 3,they are a little easier than areaid=1 because there are only one value in data1. The final results are something like the following dataset. areaid x1 y1 date x y 1 1.22 1.32 3/23/2004 1.2 1.3 1 1.53 2.34 3/22/2004 1.2 1.3 1 1.21 1.37 3/23/2004 1.5 2.3 1 1.52 2.35 3/22/2004 1.5 2.3 2 0.21 3.33 4/23/2004 0.2 3.3 2 0.23 3.35 4/23/2004 0.2 3.3 3 1.57 1.31 5/22/2004 1.5 1.3 3 1.59 1.33 5/22/2004 1.5 1.3 Any suggestions or help are greatly appreciated. Thanks a lot. [[alternative HTML version deleted]] ______________________________________________ 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.