Make unspecified correlations default to 0

[lebebr01]

sim_arguments <- list(formula = y ~ 1 + act + gpa + commute_time, 
                 fixed = list(act = list(var_type = 'ordinal',
                                         levels = 15:36),
                              gpa = list(var_type = 'continuous',
                                         mean = 2, 
                                         sd = .5),
                              commute_time = list(var_type = 'continuous',
                                         mean = 15, 
                                         sd = 6)),
                 correlate = list(fixed = data.frame(x = c('act', 'act'), 
                                                     y = c('gpa', 'commute_time'), 
                                                     corr = c(0.5, 0.6))),
                 sample_size = 1000)

simulate_fixed(data = NULL, sim_arguments) |>
  correlate_variables(sim_arguments)