Dear Rusers,
I?m tryingto figure out what I think is a pretty simple thing for anyone who
knows about correlograms.I?ve a regular grid (say 5*5 points) with some quantity
associated to eachpoint (count data). I?m trying to verify whether this quantity
is regularly /randomly or ?clusterdly? distributed on the grid. I?ve decided to
give a shotto the sp.correlogram {spdep}.
I first createda grid using cell2nb:?
grid <- cell2nb(5,5)xyc <- attr(grid,"region.id")xy
<-matrix(as.integer(unlist(strsplit(xyc, ":"))), ncol=2,
byrow=TRUE)plot(grid,xy)?>gridNeighbour list object:Number of regions: 25
Number of nonzero links: 80 Percentage nonzero weights: 12.8 Average number of
links: 3.2?I then usedsp.correlogram, and specified ?order = 4? since I figured
the maximum lagbetween 2 points on a 5 by 5 grid is 4? In sp.correlogram we do
not have tospecify a ?style? as in moran.test, not sure why so far? anyway.
results<- sp.correlogram(grid, data$quantity, order=4, method =
"I")? print(results,"bonferroni")?In the ?print? tbale, the
count ofobservation per lag order (in brakets) is 25 for each lag. This is what
I donot understand, should not this count be changing with lags? ?I mean, when
you look at the graph of ?grid? Iwould have expected a lower number for lag 4
(say only 15 pairs of observationare ?that far?) and a way higher number for lag
1? Does that make sens toanyone??regards
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