distance: Writes distance matrices In sphet: Estimation of Spatial Autoregressive Models with and without Heteroscedasticity

Description

Reads points coordinates and generates objects of class `distance.matrix`

Usage

 ```1 2 3 4 5``` ```distance(coord,region.id=NULL,output=TRUE, type=c("NN","distance","inverse"), measure=c("euclidean","gcircle","chebyshev","braycur","canberra"), nn=6, cutoff=FALSE, miles=TRUE,R=NULL, shape.name=NULL,region.id.name=NULL, firstline=FALSE,file.name=NULL) ```

Arguments

 `coord` a matrix with the (X,Y)-coordinates of the points. The first column can be the region.id variable giving the ordering of the observations `region.id` variable that defines the ordering of the observations `output` when TRUE (default) writes the object to a file `type` one of `("NN","distance","inverse")`. Nearest neighbors, distance or inverse distance `measure` one of `("euclidean","gcircle","chebyshev","braycur","canberra")`.The distance measure to be employed in the calculations. `nn` the number of nearest neighbors `cutoff` If type is `distance` or `inverse`. Assumes values 1, 2 or 3. When 1, the cutoff is set to the first quantile of the distribution of distances. When 2 to the median, and when 3 to the third quantile. Only observations with distance less than cutoff distance are neighbors. `miles` If TRUE (default), distances are in miles, otherwise in Km. (See `spDists` wcich returns km, and are converted if required) `R` deprecated, `spDists` uses an approximation to the WGS84 spheroid `shape.name` The name of the shape file. See Details `region.id.name` The name of the `region.id` variable. See Details `firstline` If `TRUE`, a first line is added to the output file. See Details `file.name` If `output`, the name of the output file. See Details

Details

The object created is similar to the content of a `'GWT'` file. The output file can be of any format. In particular, it could be a `'GWT'` file. When `firstline` is `TRUE`, an header line is added to the `'GWT'` file. The first element is simply a place holder, the second is the number of observations. The name of the shape file and of the id variable can be specified by the options `shape.name` and `region.id.name` respectively. The function performs a series of test on the `region.id` variable. If a `region.id` variable is not specified and `coord` only has two columns, a sequence from 1 to the number of observations is generated and used as identification variable. If `region.id` is specified and the first column of `coord` contains an id variable they should be the same.

Value

A `matrix` of three columns: `from`, `to`, and `distance`

Author(s)

Gianfranco Piras [email protected]

Examples

 ```1 2 3 4 5``` ```X<-runif(100,0,70) Y<-runif(100,-30,20) coord1<-cbind(seq(1,100),X,Y) thm2 <- distance(coord1,region.id=NULL,output=FALSE,type="NN", nn=6) thm2 <- distance(coord1,region.id=NULL,output=FALSE,type="distance", cutoff=1) ```

sphet documentation built on March 18, 2018, 2:05 p.m.