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how to get my subset?
2 messages · zhijie zhang, Roger Bivand
On Sun, 9 Apr 2006, zhijie zhang wrote:
Dear friends, I want to do some simulations on Moran's I, but met some problems with subset my dataset: First step: generate my dataset *x<-rnorm(20)* # generate my attribute data *y<-cell2nb(4,5)* # generate my neighbor object Then my dataset comprise with x(attribute data) and y(position). Second step:subset my datset I don't have any idea on how to get my subset, which is from two different sampling on my generated data: 1.random sampling: sample 4 data randomly from my generated data;
x<-rnorm(20) y<-cell2nb(4,5) s1 <- sample(1:length(x), 4) x_s1 <- x[s1] y_s1 <- subset(y, 1:length(x) %in% s1) (but with such a small sample, very few neighbour links will remain)
2.systematic sampling: Suppose the space is 1, the the subset should be like the following: y:1 3rows,1 3 5colums x: the correspding attribute data
look at attr(y, "region.id") to choose the subset, do:
rc <- do.call("rbind", strsplit(attr(y, "region.id"), ":"))
to extract the IDs as a character row, column matrix.
I'm not sure why sampling is useful here, simulations on Moran's I are
usually done by permutations on the x values, for example by
permutation bootstrap. There are examples among other places in
the DCluster and spdep packages, in spdep in the example to function
moran.mc().
I thought it maybe need to use index to get it , or some other better methods. I still can't get it through till now, could anybody help me? Any suggestions or help would be greatly appreciated1 -- Kind Regards,Zhi Jie,Zhang ,PHD Department of EpidemiologySchool of Public HealthFudan UniversityTel:86-21-54237149 [[alternative HTML version deleted]]
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Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no