Check that a hypothesis string uses only model parameters and arithmetic

brms::hypothesis() evaluates its string as R code, so any function call typed into a hypothesis box runs on the server. This check parses each side of a single =, ==, <, or > relation and accepts only parameter names, numeric constants, and the operators + - * / ^ ( :.

Usage

is_safe_hypothesis(x, params)

Arguments

x

Hypothesis string such as "level_AB > 0".

params

Parameter names of the fitted model, for example brms::variables(fit); names with and without the b_ prefix are both accepted.

Value

Logical scalar.

Examples

is_safe_hypothesis("level_AB > 0", c("b_Intercept", "b_level_AB"))
#> [1] TRUE
is_safe_hypothesis("level_AB*0 + q() = 0", "b_level_AB")
#> [1] FALSE