xytrend {mefa} | R Documentation |
Makes trend surface using third-degree polynomial of spatial terms.
xytrend(xy)
xy |
a matrix with 2 columns for x and y coordinates. |
The x and y coordinates are standardized (scaled to zero mean and unit variance) by the function decostand
. Polynomial terms are: $x$, $y$, $x^2$, $xy$, $y^2$, $x^3$, $x^2*y$, $x*y^2$, $y^3$, according to Legendre (1993).
A matrix with.
Peter Solymos, Solymos.Peter@aotk.szie.hu, http://www.univet.hu/users/psolymos/personal/
Legendre, P. 1993. Spatial autocorrelation: trouble or new paradigm? Ecology 74, 1659–1673.
(xy <- cbind(rnorm(20)+100, rnorm(20)-100)) (xy2 <- xytrend(xy))