Hello List,
I am not sure that I have the correct terminology here (restricted
bootstrap) which may be hampering my archive searches. I have quite a large
spatially autocorrelated data set. I have xy coordinates and the
corresponding pairwise distance matrix (metres) for each row. I would like
to randomly sample some number of rows but restricting samples such that the
distance between them is larger than the threshold of autocorrelation. I
have been been unsuccessfully trying to link the 'sample' function to values
in the distance matrix.
My end goal is to randomly sample M thousand rows of data N thousand times
calculating linear regression coefficients for each sample but am stuck on
taking the initial sample. I believe I can figure out the rest.
Example Question
I would like to radomly sample 3 rows further but withe the restriction that
they are greater than 100m apart
example data:
main data:
y<- c(1, 2, 9, 5, 6)
x<-c( 1, 3, 5, 7, 9)
z<-c(2, 4, 6, 8, 10)
a<-c(3, 9, 6, 4 ,4)
maindata<-cbind(y, x, z, a)
y x x a
[1,] 1 1 1 3
[2,] 2 3 3 9
[3,] 9 5 5 6
[4,] 5 7 7 4
[5,] 6 9 9 4
distance matrix:
row1<-c(0, 123, 567, 89)
row2<-c(98, 0, 345, 543)
row3<-c(765, 90, 0, 987)
row4<-c(654, 8, 99, 0)
dist<-rbind(row1, row2, row3, row4)
[,1] [,2] [,3] [,4]
row1 0 123 567 89
row2 98 0 345 543
row3 765 90 0 987
row4 654 8 99 0
Thanks for all of the help in the past and now
Cheers
Grant
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