corHF(value, form)
value
|
an optional vector with the parameter values. Default is
numeric(0) , which results in a vector of zeros of appropriate
dimension being assigned to the parameters when object is
initialized (corresponding to an identity correlation structure).
|
form
|
a one sided formula of the form ~ t , or code{~ t |
g}, specifying a time covariate t and, optionally, a
grouping factor g . A covariate for this correlation structure
must be integer valued. 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.
|
corHF
class,
representing a correlation structure satisfying the Huyn-Feldt
conditions r(i,j)=g(i)+g(j)+(1-2*g(i))*d(i,j),
where r(i,j) denotes the
correlation between observations i
and j
,
g(i) and g(j) are the corresponding
parameter values, and d(i,j) is an indicator
variable assuming value 1 when i=j and 0
otherwise. Objects created using this constructor need to be later
initialized using the appropriate initialize
method.corHF
, representing an Huyn-Feldt
correlation structure.initialize.corHF
library(lme) ## covariate is observation order and grouping factor is Subject cs1 <- corHF(form = ~ 1 | Subject)