# corBlomberg

##### Blomberg et al.'s Correlation Structure

The ``ACDC'' (accelerated/decelerated) model assumes that continuous traits evolve under a Brownian motion model which rates accelerates (if \(g\) < 1) or decelerates (if \(g\) > 1) through time. If \(g\) = 1, then the model reduces to a Brownian motion model.

- Keywords
- models

##### Usage

```
corBlomberg(value, phy, form = ~1, fixed = FALSE)
# S3 method for corBlomberg
corMatrix(object, covariate = getCovariate(object),
corr = TRUE, ...)
# S3 method for corBlomberg
coef(object, unconstrained = TRUE, …)
```

##### Arguments

- value
the (initial) value of the parameter \(g\).

- phy
an object of class

`"phylo"`

.- form
a one sided formula of the form ~ t, or ~ t | g, specifying the taxa covariate t and, optionally, a grouping factor g. A covariate for this correlation structure must be character valued, with entries matching the tip labels in the phylogenetic tree. When a grouping factor is present in form, the correlation structure is assumed to apply only to observations within the same grouping level; observations with different grouping levels are assumed to be uncorrelated. Defaults to ~ 1, which corresponds to using the order of the observations in the data as a covariate, and no groups.

- fixed
a logical specifying whether

`gls`

should estimate \(\gamma\) (the default) or keep it fixed.- object
an (initialized) object of class

`"corBlomberg"`

.- covariate
an optional covariate vector (matrix), or list of covariate vectors (matrices), at which values the correlation matrix, or list of correlation matrices, are to be evaluated. Defaults to getCovariate(object).

- corr
a logical value specifying whether to return the correlation matrix (the default) or the variance-covariance matrix.

- unconstrained
a logical value. If

`TRUE`

(the default), the coefficients are returned in unconstrained form (the same used in the optimization algorithm). If`FALSE`

the coefficients are returned in ``natural'', possibly constrained, form.- …
further arguments passed to or from other methods.

##### Value

an object of class `"corBlomberg"`

, the coefficients from an
object of this class, or the correlation matrix of an initialized
object of this class. In most situations, only `corBlomberg`

will
be called by the user.

##### References

Blomberg, S. P., Garland, Jr, T., and Ives, A. R. (2003) Testing for
phylogenetic signal in comparative data: behavioral traits are more
labile. *Evolution*, **57**, 717--745.

*Documentation reproduced from package ape, version 5.4, License: GPL-2 | GPL-3*