Tjostheim's Coefficient
Computes Tjostheim's coefficient for two spatial sequences observed over the same locations on the plane.
cor.spatial(x, y, coords)
x |
an |
y |
an |
coords |
an |
The implemented technique is a nonparametric coefficient that summarizes the
association between two spatial variables. This coefficient was first introduced
by Tjostheim (1978) and later generalized by Hubert and Golledge (1992). The
computation of the coefficient is based on the construction of ranks associated
to suitable modifications of the coordinates. Tjostheim's coefficient is a variant
of the correlation coefficient (cor) to be used in a spatial statistics
context.
Tjostheim's coefficient. The variance is returned as the attribute "variance".
Tjostheim, D., (1978), A measure of association for spatial variables. Biometrika 65, 109–114.
Hubert, L., Golledge, R.G., (1982), Measuring association between spatially defined variables: Tjostheim's coefficient index and some extensions. Geographical Analysis 14, 273–278.
# Murray Smelter site dataset
data(murray)
# defining the arsenic (As) and lead (Pb) variables from the murray dataset
x <- murray$As
y <- murray$Pb
# extracting the coordinates from Murray dataset
coords <- murray[c("xpos","ypos")]
# computing Tjostheim's coefficient
z <- cor.spatial(x, y, coords)
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