[R] how to store estimates results as scalars of a matrix?
Uwe Ligges
ligges at statistik.uni-dortmund.de
Sat Jun 19 13:38:02 CEST 2004
Joao Pedro W. de Azevedo wrote:
> Dear R users,
>
> I've written a loop to generate Moran's test (spdep package) on serval
> subsamples of a large dataset. See below a short example.
>
> My loop is working fine, however I would like to be able to store the test
> results as lines of a matrix, that I would latter be able to export as a
> dataset. My problem is that I'm not sure how I could do this using R.
>
> Any help will be much appreciated.
>
> All the very best,
>
> JP
>
>
>
> coords2 <- as.matrix(jcdist.data[1:87, 6:7])
>
> col.tri.nb<-tri2nb(coords2)
>
> for(n in c(1,88,175,262,349)) {
> f<- n+86
> work <- jcdist.data[n:f, 10:12]
>
> res <-moran.test(spNamedVec("res1", work), nb2listw(col.tri.nb,
> style="W"))
> moran<-res$estimate[1]
> upper<-res$estimate[1] + (qnorm(0.025, lower.tail=FALSE)
> *sqrt(res$estimate[3]))
> lower<-res$estimate[1] - (qnorm(0.025, lower.tail=FALSE)
> *sqrt(res$estimate[3]))
>
> print(moran)
> print(upper)
> print(lower)
[...]
> }
What you really want is something along the lines (untested!):
coords2 <- as.matrix(jcdist.data[1:87, 6:7])
col.tri.nb <- tri2nb(coords2)
N <- c(1, 88, 175, 262, 349)
# generate the transposed matrix of results, because
# it is faster to assign into columns rathger than into rows:
results <- mattrix(nrow = 3, ncol = length(N))
# the following calculations shouldn't be done within the loop -
# efficiency!
f <- N + 86
qn <- qnorm(0.025, lower.tail = FALSE)
for(i in seq(along = N)) {
work <- jcdist.data[n[i]:f[i], 10:12]
res <- moran.test(spNamedVec("res1", work),
nb2listw(col.tri.nb, style = "W"))
# calculate the following just once:
ci <- qn * sqrt(res$estimate[3])
results[,i] <- res$estimate[1] + c(1, ci, -ci)
}
t(results)
colnames(results) <- c("Moran", "upper", "lower")
Uwe Ligges
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