localmoran.sad {spdep} | R Documentation |
The function implements Tiefelsdorf's application of the Saddlepoint
approximation to local Moran's Ii's reference distribution. Tests are
reported for separately for each zone selected, and may be summarised
using summary.localmoransad
. Values of local Moran's Ii
agree with those from localmoran()
, but in that function, the
standard deviate - here the Saddlepoint approximation - is based on the
randomisation assumption.
localmoran.sad(model, select, nb, glist=NULL, style="W", zero.policy=FALSE, alternative="greater", spChk=NULL, save.Vi=FALSE) as.data.frame.localmoransad(x, row.names=NULL, optional=FALSE) print.localmoransad(x, ...) summary.localmoransad(object, ...) print.summary.localmoransad(x, ...) listw2star(listw, ireg, style, n, D, a, zero.policy=FALSE)
model |
an object of class lm returned by lm ; weights
and offsets should not be used |
select |
an integer vector of the id. numbers of zones to be tested |
nb |
a list of neighbours of class nb |
glist |
a list of general weights corresponding to neighbours |
style |
can take values W, B, C, and S |
zero.policy |
if TRUE assign zero to the lagged value of zones without neighbours, if FALSE assign NA |
alternative |
a character string specifying the alternative hypothesis, must be one of greater (default), less or two.sided. |
spChk |
should the data vector names be checked against the spatial objects for identity integrity, TRUE, or FALSE, default NULL to use get.spChkOption() |
save.Vi |
if TRUE, return the star-shaped weights lists for each zone tested |
x |
object to be printed |
row.names |
ignored argument to as.data.frame.localmoransad ;
row names assigned from localmoransad object |
optional |
ignored argument to as.data.frame.localmoransad ;
row names assigned from localmoransad object |
object |
object to be summarised |
... |
arguments to be passed through |
listw |
a listw object created for example by nb2listw |
ireg |
a zone number |
n |
internal value depending on listw and style |
D |
internal value depending on listw and style |
a |
internal value depending on listw and style |
The function implements the analytical eigenvalue calculation together with trace shortcuts given or suggested in Tiefelsdorf (2002), partly following remarks by J. Keith Ord, and uses the Saddlepoint analytical solution from Tiefelsdorf's SPSS code. No n by n matrices are needed at any point, the star-shaped weights matrices being handled as listw lists.
A list with class localmoransad
containing "select" lists, each with
class moransad
with the following components:
statistic |
the value of the saddlepoint approximation of the standard deviate of local Moran's Ii. |
p.value |
the p-value of the test. |
estimate |
the value of the observed local Moran's Ii. |
alternative |
a character string describing the alternative hypothesis. |
method |
a character string giving the method used. |
data.name |
a character string giving the name(s) of the data. |
internal1 |
Saddlepoint omega, r and u |
df |
degrees of freedom |
tau |
maximum and minimum analytical eigenvalues |
i |
zone tested |
Roger Bivand Roger.Bivand@nhh.no
Tiefelsdorf, M. 2002 The Saddlepoint approximation of Moran's I and local Moran's Ii reference distributions and their numerical evaluation. Geographical Analysis, 34, pp. 187206; see also Tiefelsdorf's SPSS code: http://geog-www.sbs.ohio-state.edu/faculty/tiefelsdorf/GeoStat.htm.
localmoran
, lm.morantest
,
lm.morantest.sad
data(eire) e.lm <- lm(OWNCONS ~ ROADACC, data=eire.df) e.locmor <- summary(localmoran.sad(e.lm, eire.nb, select=1:nrow(eire.df))) mean(e.locmor[,1]) lm.morantest(e.lm, nb2listw(eire.nb))