distmatrix {cshapes} | R Documentation |
This function computes a distance matrix for the given date. It selects all the active CShapes polygons, determines their distances and outputs a distance matrix in kilometers. The function can compute different types of distance matrices, specified by the "type" parameter: (i) capital distances, and (ii) centroid distances, and (iii) minimum distances between polygons. The latter computation is very expensive if polygons have many nodes. For that reason, the function provides two different minimum distance computations: "mindist.simple" (the default), which is run on a simplified set of country polygons with fewer nodes, and "mindist.full", which is run on the normal set of polygons.
distmatrix(date, type="mindist", tolerance=0.1, useGW=T)
date |
The date for which the distance matrix should be computed. This argument must be of type Date and must be in the range 1/1/1946 - 30/6/2008. |
type |
Specifies the type of distance matrix: capdist for capital distances, centdist for centroid distances, and mindist for minimum distances. |
useGW |
Boolean argument specifying the system membership coding. TRUE (Default): Gleditsch and Ward (1999). FALSE: Correlates of War. |
tolerance |
Tolerance for polygon simplification according the the Douglas-Peuckert algorithm. Only used for mindist computation (type="mindist"). |
A quadratic weights matrix, with the row and column labels containing the country identifiers in the specified coding system (COW or G&W).
Nils B. Weidmann
# Compute a matrix of minimum distances # for the international system on 1/1/2008 # using the Correlates of War list and the default accuracy wmat <- distmatrix(as.Date("2008-1-1"), type="capdist", useGW=FALSE) # For model estimation, our matrix should contain # the inverted distances wmat <- 1/wmat # Fix the Inf values along the diagonale diag(wmat) <- 0