Random-effect scale formula syntax

sd(group) ~ predictors and its siblings are formula-only syntax for modelling random-effect standard deviations. They are captured by drm_formula() or bf() and are not evaluated as ordinary R calls. In particular, sd(group) ~ predictors does not replace stats::sd().

Value

A formula-syntax reference page; no object is returned.

Details

The currently documented syntax is:

• sd(group) ~ predictors for univariate Gaussian location random-effect scale models;

• sd1(group) ~ predictors and sd2(group) ~ predictors for bivariate Gaussian location random-effect scale models targeting mu1 and mu2;

• sd_phylo(species) ~ predictors for univariate Gaussian phylogenetic location random-effect scale models;

• sd_phylo1(species) ~ predictors and sd_phylo2(species) ~ predictors for bivariate Gaussian phylogenetic location random-effect scale models targeting mu1 and mu2.

These formulas model the standard deviation of a latent random-effect block. They are distinct from residual scale formulas such as sigma ~ predictors and from latent correlation formulas such as corpair(). Non-Gaussian random-effect scale formulas, spatial direct-SD formulas, and explicit coefficient-specific targets such as sd(group, dpar = "mu", coef = "slope") ~ predictors remain planned.

Examples

bf(y ~ x + (1 | id), sigma ~ z, sd(id) ~ habitat)
#> <drm_formula>
#> y ~ x + (1 | id)
#> sigma ~ z
#> sd(id) ~ habitat

bf(
  mu1 = y1 ~ x + (1 | p | id),
  mu2 = y2 ~ x + (1 | p | id),
  sd1(id) ~ habitat,
  sd2(id) ~ habitat,
  rho12 = ~ x
)
#> <drm_formula>
#> mu1 = y1 ~ x + (1 | p | id)
#> mu2 = y2 ~ x + (1 | p | id)
#> sd1(id) ~ habitat
#> sd2(id) ~ habitat
#> rho12 = ~x

bf(
  y ~ x + phylo(1 | species, tree = tree),
  sd_phylo(species) ~ ecology
)
#> <drm_formula>
#> y ~ x + phylo(1 | species, tree = tree)
#> sd_phylo(species) ~ ecology