| createAdj {season} | R Documentation |
Creates an Adjacency Matrix
Description
Creates an adjacency matrix in a form suitable for using in BRugs or
WinBUGS.
Usage
createAdj(matrix, filename = "Adj.txt", suffix = NULL)
Arguments
matrix |
square matrix with 1's for neighbours and NA's for non-neighbours. |
filename |
filename that the adjacency matrix file will be written to (default=‘Adj.txt’). |
suffix |
string to be appended to ‘num’, ‘adj’ and ‘weights’ object names |
Details
Adjacency matrices are used by conditional autoregressive (CAR) models to smooth estimates according to some neighbourhood map. The basic idea is that neighbouring areas have more in common than non-neighbouring areas and so will be positively correlated.
As well as correlations in space it is possible to use CAR models to model similarities in time.
In this case the matrix represents those time points that we wish to assume to be correlated.
Value
Creates a text file named filename that contains the total
number of neighbours (num), the index number of the adjacent neighbours
(adj) and the weights (weights).
Author(s)
Adrian Barnett a.barnett@qut.edu.au
Examples
# Nearest neighbour matrix for 5 time points
x = c(NA,1,NA,NA,NA)
(V = toeplitz(x))
createAdj(V)