Hi Rusers, I found sometimes that the same values cannot be judged to be the same in R. Anybody knows the probelm? I think i ignored some minor detail. Thanks. Here is the example. ############ 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") 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$tag<-0 data1_1<-data1[1,] data2_1<-data2[data2$areaid==data1_1$areaid & data2$tag==0,] ran_1<-sample(c(1:length(data2_1)),2, replace = FALSE) data2_1<-data2_1[ran_1,] data_1<-merge(data1_1,data2_1) #data_1 # areaid x y date x1 y1 tag # 1 1 1.2 1.3 3/23/2004 1.52 2.35 0 # 2 1 1.2 1.3 3/23/2004 1.53 2.34 0 data2[data_1$x1==data2$x1 & data_1$y1==data2$y1 & data2$tag==0,] #data2[c(data_1$x1==data2$x1 & data_1$y1==data2$y1 & data2$tag==0),] # areaid x1 y1 tag #2 1 1.53 2.34 0 There should be two same observations between data_1 and data2, but here only one was identified. Thanks a lot.
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