This function is a constructor for the cor_arma class,
allowing for moving average terms only.
cor_ma(formula = ~1, q = 1, cov = FALSE)A one sided formula of the form ~ t, or ~ 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 formula, 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.
A non-negative integer specifying the moving average (MA) order of the ARMA structure. Default is 0.
A flag indicating whether ARMA effects should be estimated
by means of residual covariance matrices
(currently only possible for stationary ARMA effects of order 1).
If FALSE (the default) a regression formulation
is used that is considerably faster and allows for ARMA effects
of order higher than 1 but cannot handle user defined standard errors.
An object of class cor_arma containing solely moving average terms.
# NOT RUN {
cor_ma(~visit|patient, q = 2)
# }
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