mu and alpha are parameters.

How to implement this inequaliity constrait in Stan?

so that mu1*alpha1>0 and mu2*alpha2>0

Thank you very much.

with regards

# How to add inequality constraint on the model

**jun_cai**#1

**bgoodri**#2

```
parameters {
real mu_1;
real<lower=0> mu_1_alpha_1;
}
transformed parameters {
real sigma_1 = mu_1_alpha_1 / mu_1;
}
```

**jun_cai**#3

Thank you very much!

what is sigma_1?

should i do something like this?

‘parameters {’

‘vector[4]p;’

‘real<lower=0> mu_1_alpha_1= p[1]*p[2] ;’

‘real<lower=0> mu_2_alpha_2= p[3]*p[4] ;’

‘}’

p is the vector of paramters. p[1]=mu_1,p[2]=alpha_1,p[3]=mu_2,p[4]=alpha_2

Thank you very much!

with best regards

**jun_cai**#6

i have this warning, do you know why this happened.

anon_model.stan (578 Bytes)

compile: DIAGNOSTIC(S) FROM PARSER:

compile: Warning (non-fatal):

compile: Left-hand side of sampling statement (~) may contain a non-linear transform of a parameter or local variable.

compile: If it does, you need to include a target += statement with the log absolute determinant of the Jacobian of the transform.

compile: Left-hand-side of sampling statement:

compile: b1 ~ normal(…)

compile: Warning (non-fatal):

compile: Left-hand side of sampling statement (~) may contain a non-linear transform of a parameter or local variable.

compile: If it does, you need to include a target += statement with the log absolute determinant of the Jacobian of the transform.

compile: Left-hand-side of sampling statement:

compile: b2 ~ normal(…)

ogden-2: Informational Message: The current Metropolis proposal is about to be rejected because of the following issue:

ogden-2: Exception: multi_normal_lpdf: Location parameter[2] is -inf, but must be finite! (in ‘E://anon_model.stan’ at line 30)

ogden-2: If this warning occurs sporadically, such as for highly constrained variable types like covariance matrices, then the sampler is fine,

ogden-2: but if this warning occurs often then your model may be either severely ill-conditioned or misspecified.