Help: plot part of the correlogram
On Tue, 3 Apr 2012, ??? wrote:
Hi eveybody, I want to test the local sptial autocorrelation of my data
(present and absence). My study area is about 16410 km square. I used
correlog {ncf} to plot a correlogram. I want t set a lower increment.
for example 200 meters. And I got a correlogram with many bins, which is
not readable. So i hope i can just plot part of them, for example the
first 50 points. From the achieve, i found that it can be conducted by
"plot(XXX$correlation[1:50])". but it does not show the significance
test. Can anybody help me plot such a map? or can we receive the P value
of the first 50 points as we received the moran's I value? Thank you
very much! Sincerely Xiaoma Li
Please learn about str() to see the internal structure of objects: library(ncf) x <- expand.grid(1:20, 1:5)[,1] y <- expand.grid(1:20, 1:5)[,2] z <- rmvn.spa(x=x, y=y, p=2, method="exp"), fit1 <- correlog(x=x, y=y, z=z[,1], increment=0.1, resamp=1000) plot(fit1) str(fit1) # fit1 is a list of class "correlog", with vector components of equal # length. One is p, so: fit1$p # are the apparent p-values (uncorrected for multiple comparisons I think, # computed by permutation) IMO not to be trusted especially for narrow # increments class(fit1) <- NULL df1 <- as.data.frame(fit1) fit2 <- as.list(df1[1:50,]) str(fit2) class(fit2) <- "correlog" # reconstruct object as class "correlog" after selecting rows from # data.frame plot(fit2) Hope this helps, Roger
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Roger Bivand Department of Economics, NHH Norwegian School of Economics, 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