# [R-sig-Geo] Problem for plotting Moran's I estimates

Roger Bivand Roger.Bivand at nhh.no
Tue Mar 29 19:37:20 CEST 2005

```On Tue, 29 Mar 2005, Chloe ARCHINARD wrote:

> Hello all, I'm a new user of R and I have used the spdep package to
> calculate Moran's I estimates. I used the dnearneigh() function and
> moran.test() function and obtained what I wanted, but now I want to plot
> my results with the p-values. I regrouped my results for the Moran's I
> like
> >m=c(m1\$e,m2\$e...)        #m1 contain the results of the moran.test for lag1
> >p=c(m1\$p.v,m2\$p.v...)
> The problem is that in mx\$e there are three values (moran'I statistic,
> expectation and variance) and when I plot my results I plot all the
> three values for each lag. What should I do to choose only the statistic
> for plotting and maybe the variance for each I statistic? (For the
> p-value it's ok I have found how to differentiate the significant and
> non significant values.) I hope someone understand my question and could
> help me! Thanks a lot.

If you have the output object from moran.test()

data(oldcol)
res <- moran.test(COL.OLD\$CRIME, nb2listw(COL.nb))
str(res) # shows the structure of the object
est <- res\$estimate[1]
pv <- res\$p.value

I suggest you make a list of test result objects for your distance lags,
and then use sapply(mylist, function(x) c(x\$estimate[1], x\$p.value)) to
extract the values (you may need t() around the result to transpose the
output). I'll try to add an example like this to moran.test() - any
suggestions of a well-known suitable data set with known Moran's I values
and distance bands?

Roger

>
> Chloé ARCHINARD
> Centre d'Ecologie Fonctionnelle et Evolutive
> (C.N.R.S.-U.M.R. 5175)
> 1919, Route de Mende
> 34293 Montpellier Cedex 5 France
> chloe.archinard at cefe.cnrs.fr
>
>
>

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of