A list, will be initialized after an instance is built. "r"
stands for random variable or closed form used in the expression of y,
"o" stands for others. This value only affects the string representation of
the object. If a variable is not part of the expression of y, then it
should be labelled as "o". If a variable is part of the expression of y,
but it is not a random variable or a closed form expression, then it should
be labelled as "o" as well.
Examples
# Instantiate
x <- rand_uniform()
e <- rand_normal()
test <- vi_model(prm = list(x = x, e = e),
prm_type = list(x = "r", e = "r"),
formula = y ~ 1 + x + x^2 + e)
test$prm_type
#> $x
#> [1] "r"
#>
#> $e
#> [1] "r"
#>