Helper functions to specify linear and non-linear
formulas for use with brmsformula.
nlf(formula, ..., flist = NULL, dpar = NULL)lf(..., flist = NULL, dpar = NULL)
set_nl(nl = TRUE, dpar = NULL)
Non-linear formula for a distributional parameter.
The name of the distributional parameter can either be specified
on the left-hand side of formula or via argument dpar.
Additional formula objects to specify
predictors of non-linear and distributional parameters.
Formulas can either be named directly or contain
names on their left-hand side.
The following are distributional parameters of specific families
(all other parameters are treated as non-linear parameters):
sigma (residual standard deviation or scale of
the gaussian, student, lognormal
exgaussian, and asym_laplace families);
shape (shape parameter of the Gamma,
weibull, negbinomial, and related
zero-inflated / hurdle families); nu
(degrees of freedom parameter of the student family);
phi (precision parameter of the beta
and zero_inflated_beta families);
kappa (precision parameter of the von_mises family);
beta (mean parameter of the exponential componenent
of the exgaussian family);
quantile (quantile parameter of the asym_laplace family);
zi (zero-inflation probability);
hu (hurdle probability);
zoi (zero-one-inflation probability);
coi (conditional one-inflation probability);
disc (discrimination) for ordinal models;
bs, ndt, and bias (boundary separation,
non-decision time, and initial bias of the wiener
diffusion model).
All distributional parameters are modeled
on the log or logit scale to ensure correct definition
intervals after transformation.
See 'Details' for more explanation.
Optional list of formulas, which are treated in the
same way as formulas passed via the ... argument.
Optional character string specifying the distributional
parameter to which the formulas passed via ... and
flist belong.
Logical; Indicates whether formula should be
treated as specifying a non-linear model. By default, formula
is treated as an ordinary linear model formula.
For lf and nlf a list that can be
passed to brmsformula or added
to an existing brmsformula object. For set_nl
a list that can be added to an existing
brmsformula object.
# NOT RUN {
# add more formulas to the model
bf(y ~ 1) +
nlf(sigma ~ a * exp(b * x), a ~ x) +
lf(b ~ z + (1|g), dpar = "sigma") +
gaussian()
# specify 'nl' later on
bf(y ~ a * inv_logit(x * b)) +
lf(a + b ~ z) +
set_nl(TRUE)
# }
Run the code above in your browser using DataCamp Workspace