misolationmap {GeoXp}R Documentation

Interactive multivariate isolation plot and map

Description

The function misolationmap draws a scatterplot with the pairwise Mahalanobis distances between the observations and their neighbors on the y-axis and the "degree of isolation" of the observations on the x-axis and a map

Usage

misolationmap(long, lat, object,propneighb=0.4,chisqqu=0.975, listvar=NULL, listnomvar=NULL, criteria=NULL,
carte = NULL, label = "",cex.lab=1,pch = 16,col="blue", xlab = "degree of isolation",
ylab="Pairwise Mahalanobis distances", lablong = "", lablat = "", axes=FALSE)

Arguments

long a vector x of size n
lat a vector y of size n
object a spatial weight matrix of class nb
propneighb proportion of neighbors included in ellipsoid
chisqqu value of alpha for the definition of global outliers
listvar matrix of variables which permit to add graphics such as histogram, etc. and plot bubbles on map using the tlclk window
listnomvar names of variables from listvar
criteria a vector of size n of boolean which permit to represent preselected sites with a cross, using the tcltk window
carte matrix with 2 columns for drawing spatial polygonal contours : x and y coordinates of the vertices of the polygon
label a list of character of size n with name of site. Names are printed on map after a selection
cex.lab character size of label
pch 16 by default, symbol for selected points
col "blue" by default, color of the points on the two graphics
xlab a title for the graphic x-axis
ylab a title for the graphic y-axis
lablong name of the x-axis that will be printed on the map
lablat name of the y-axis that will be printed on the map
axes TRUE for drawing axes on the map

Details

The pairwise Mahalanobis distances are calculated using the robust Minimum Covariance Determinant (MCD) estimator associated with 75% of observations (function covMcd in the robustbase package). For each observation, the degree of isolation is a chi-square quantile of the conditional distribution of the pairwise Mahalanobis distances associated with the ellipsoid containing the proportion propneighb of neighbors. The parameter propneighb gives the proportion of neighbors that is expected to be quite similar to the observation in order to conclude that the observation is not a local outlier. Under independence and normality conditions, the user can expect a degree of isolation close by the parameter propneighb (vertical line on the scatterplot). An observation with a high degree of isolation is suspected to be a local outlier. Users have also the possibility to plot bubbles on the map which size depends on the robust Mahalanobis distance of each observation to the center of the distribution (function arw in the package mvoutlier).

Value

A matrix of boolean of size n x n

Author(s)

Fizmoser P., Thomas-Agnan C., Ruiz-Gazen A., Laurent T.,

References

Aragon Yves, Perrin Olivier, Ruiz-Gazen Anne, Thomas-Agnan Christine (2009), Statistique et Econométrie pour données géoréférencées : modèles et études de cas

See Also

mvariocloudmap

Examples

data(moss)
data(kola.background)
xy <- moss[,c("XCOO","YCOO")]
xy.knn <- knearneigh(as.matrix(xy), k=15)
#xy.knn <- dnearneigh(as.matrix(xy), 0,50000 )

nb.kola <- knn2nb(xy.knn)
dat.kola <- log10(moss[, c("Ag","As","Bi","Cd","Co","Cu","Ni")])

obs<-misolationmap(xy$XCOO,xy$YCOO,nb.kola,propneighb=0.40,chisqqu=0.975,dat.kola,names(dat.kola),col='royalblue',pch=7,
carte= kola.background,cex.lab=0.7)


[Package GeoXp version 1.4 Index]