# Constrain error for inv_logit

Hello, I am modelling correlated binary outcomes using my own distribution. However when I use inv_logit for my probabilities take values outside 0 and 1 even if i set up constrains for p and used my own initial values.

Any ideas???

``````transformed parameters{
real<lower = -1, upper = 1> rho1;
real ktau1;
vector<lower = 0, upper = 1> pA[Ns];
vector<lower = 0, upper = 1> pB[Ns];
matrix[2,2] Sigma;
//rho1 = tanh(etarho1);
rho1   = etarho1*2-1;
for (i in 1:Ns){
pA[i] = inv_logit(mu1[i]);
pA[i] = inv_logit(mu2[i]);
pB[i] = inv_logit(mu1[i]+delta[i,1]);
pB[i] = inv_logit(mu2[i]+delta[i,2]);
}
ktau1  = (2/pi())*asin(rho1);
Sigma[1, 1] = sigma^2;
Sigma[1, 2] = sigma*sigma*rho1;
Sigma[2, 1] = sigma*sigma*rho1;
Sigma[2, 2] = sigma^2;
}

model{
//etarho1   ~ beta(1.5,1.5);
theta     ~ uniform(-30,30);
etarho1   ~ beta(1.5,1.5);
d         ~ normal(0, 10);
sigma     ~ cauchy(0, 5);
mu1       ~ normal(0, 10);
mu2       ~ normal(0, 10);
for (i in 1:Ns){
delta[i]  ~ multi_normal(d,Sigma);
}

for(i in 1:Ns){
rA[i]  ~ BBinom(pA[i], N[i],theta);
rB[i]  ~ BBinom(pB[i], N[i],theta);
}
}
``````

Chain 1: Rejecting initial value:
Chain 1: Error evaluating the log probability at the initial value.
Chain 1: Exception: Exception: binomial_cdf: Probability parameter is 2, but must be in the interval [0, 1] (in ‘model3eb434f32c81_BB2’ at line 36)
(in ‘model3eb434f32c81_BB2’ at line 95)

Chain 1:
Chain 1: Initialization between (-2, 2) failed after 100 attempts.
Chain 1: Try specifying initial values, reducing ranges of constrained values, or reparameterizing the model.
 “Error in sampler\$call_sampler(args_list[[i]]) : Initialization failed.”
 “error occurred during calling the sampler; sampling not done”

Thanks a lot.

Can you show us the code for `BBinom`? Hard to figure out what code the error is talking about otherwise.