On Nov 12, 2009, at 10:04 PM, rusers.sh wrote:
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),]
I suspect your use of multiple logical tests across two different
dataframes with different numbers of rows may not be giving you the
results you expect:
> data_1$x1==data2$x1
[1] FALSE FALSE FALSE TRUE FALSE FALSE FALSE FALSE
> data_1$y1==data2$y1
[1] FALSE FALSE FALSE TRUE FALSE FALSE FALSE FALSE
> data2$tag==0
[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE # So that test is doing
nothing
> data2$y1
[1] 1.32 2.34 1.37 2.35 3.33 3.35 1.31 1.33
> data_1$y1
[1] 2.34 2.35
Perhaps you ought to look at the dyadic function %in% as a substitute
for "=="
?"%in%"
# 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.
If the above commentary did not clarify what was happening, then can
you explain in more detail what (and why) you were doing at each step
and what you expected to get in the end. The phrase "two same
observations between data_1 and data2" does not seem to be an
unambiguous expression. I cannot think of any natural ordering to
these rows of cases, so the notion of "between" does not seem
appropriate.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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