xytrend {mefa}R Documentation

Trend Surface for Spatial Coordinates

Description

Makes trend surface using third-degree polynomial of spatial terms.

Usage

xytrend(xy)

Arguments

xy a matrix with 2 columns for x and y coordinates.

Details

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).

Value

A matrix with.

Author(s)

Peter Solymos, Solymos.Peter@aotk.szie.hu, http://www.univet.hu/users/psolymos/personal/

References

Legendre, P. 1993. Spatial autocorrelation: trouble or new paradigm? Ecology 74, 1659–1673.

See Also

decostand

Examples

(xy <- cbind(rnorm(20)+100, rnorm(20)-100))
(xy2 <- xytrend(xy))

[Package mefa version 1.1-0 Index]