VGAM (version 1.1-9)

latvar: Latent Variables

Description

Generic function for the latent variables of a model.

Usage

latvar(object, ...)
    lv(object, ...)

Value

The value returned depends specifically on the methods function invoked.

Arguments

object

An object for which the extraction of latent variables is meaningful.

...

Other arguments fed into the specific methods function of the model. Sometimes they are fed into the methods function for Coef.

Author

Thomas W. Yee

Warning

latvar and lv are identical, but the latter will be deprecated soon.

Latent variables are not really applicable to vglm/vgam models.

Details

Latent variables occur in reduced-rank regression models, as well as in quadratic and additive ordination models. For the latter two, latent variable values are often called site scores by ecologists. Latent variables are linear combinations of the explanatory variables.

References

Yee, T. W. and Hastie, T. J. (2003). Reduced-rank vector generalized linear models. Statistical Modelling, 3, 15--41.

Yee, T. W. (2004). A new technique for maximum-likelihood canonical Gaussian ordination. Ecological Monographs, 74, 685--701.

Yee, T. W. (2006). Constrained additive ordination. Ecology, 87, 203--213.

See Also

latvar.qrrvglm, latvar.rrvglm, latvar.cao, lvplot.

Examples

if (FALSE) {
hspider[, 1:6] <- scale(hspider[, 1:6])  # Standardized environmental vars
set.seed(123)
p1 <- cao(cbind(Pardlugu, Pardmont, Pardnigr, Pardpull, Zoraspin) ~
          WaterCon + BareSand + FallTwig + CoveMoss + CoveHerb + ReflLux,
          family = poissonff, data = hspider, Rank = 1, df1.nl =
          c(Zoraspin = 2.5, 3), Bestof = 3, Crow1positive = TRUE)

var(latvar(p1))  # Scaled to unit variance  # Scaled to unit variance
c(latvar(p1))    # Estimated site scores
}