sp.correlogram

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Percentile

Spatial correlogram

Spatial correlograms for Moran's I and the autocorrelation coefficient, with print and plot helper functions.

Keywords
spatial
Usage
sp.correlogram(neighbours, var, order = 1, method = "corr", style = "W", randomisation = TRUE, zero.policy = NULL, spChk=NULL) "plot"(x, main, ylab, ylim, ...) "print"(x, p.adj.method="none", ...)
Arguments
neighbours
an object of class nb
var
a numeric vector
order
maximum lag order
method
"corr" for correlation, "I" for Moran's I, "C" for Geary's C
style
style can take values W, B, C, and S
randomisation
variance of I or C calculated under the assumption of randomisation, if FALSE normality
zero.policy
default NULL, use global option value; if FALSE stop with error for any empty neighbour sets, if TRUE permit the weights list to be formed with zero-length weights vectors
spChk
should the data vector names be checked against the spatial objects for identity integrity, TRUE, or FALSE, default NULL to use get.spChkOption()
x
an object from sp.correlogram() of class spcor
p.adj.method
correction method as in p.adjust
main
an overall title for the plot
ylab
a title for the y axis
ylim
the y limits of the plot
...
further arguments passed through
Details

The print function also calculates the standard deviates of Moran's I or Geary's C and a two-sided probability value, optionally using p.adjust to correct by the nymber of lags. The plot function plots a bar from the estimated Moran's I, or Geary's C value to +/- twice the square root of its variance (in previous releases only once, not twice). The table includes the count of included observations in brackets after the lag order. Care needs to be shown when interpreting results for few remaining included observations as lag order increases.

Value

returns a list of class spcor:

References

Cliff, A. D., Ord, J. K. 1981 Spatial processes, Pion, pp. 118--122, Martin, R. L., Oeppen, J. E. 1975 The identification of regional forecasting models using space-time correlation functions, Transactions of the Institute of British Geographers, 66, 95--118.

See Also

nblag, moran, p.adjust

Aliases
  • sp.correlogram
  • plot.spcor
  • print.spcor
Examples
example(nc.sids)
ft.SID74 <- sqrt(1000)*(sqrt(nc.sids$SID74/nc.sids$BIR74) +
  sqrt((nc.sids$SID74+1)/nc.sids$BIR74))
tr.SIDS74 <- ft.SID74*sqrt(nc.sids$BIR74)
cspc <- sp.correlogram(ncCC89_nb, tr.SIDS74, order=8, method="corr",
 zero.policy=TRUE)
print(cspc)
plot(cspc)
Ispc <- sp.correlogram(ncCC89_nb, tr.SIDS74, order=8, method="I",
 zero.policy=TRUE)
print(Ispc)
print(Ispc, "bonferroni")
plot(Ispc)
Cspc <- sp.correlogram(ncCC89_nb, tr.SIDS74, order=8, method="C",
 zero.policy=TRUE)
print(Cspc)
print(Cspc, "bonferroni")
plot(Cspc)
drop.no.neighs <- !(1:length(ncCC89_nb) %in% which(card(ncCC89_nb) == 0))
sub.ncCC89.nb <- subset(ncCC89_nb, drop.no.neighs)
plot(sp.correlogram(sub.ncCC89.nb, subset(tr.SIDS74,  drop.no.neighs),
 order=8, method="corr"))
Documentation reproduced from package spdep, version 0.6-9, License: GPL (>= 2)

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