Good day everyone in the list, please how can I constrain a discrimination parameter in stata code giving in stata Blog on Bayesian Item binary item response theory models( three-parameter logistic) such that (discrim:i.item will be equalled 1.372672)


Code:
clear mata
* Three-parameter Logistic (Bayesian approach)*
version 16.0

set maxvar 32767
use "Result_Coding.dta", clear
generate id = _n
quietly reshape long q, i(id) j(item)
rename q y
fvset base none id item
set seed 10

bayesmh y, likelihood(dbernoulli({gues:}+(1-{gues:})*            ///
invlogit({discrim:}*({subj:}-{diff:})))) ///
redefine(discrim:i.item) redefine(diff:i.item)                    ///
redefine(gues:i.item)    redefine(subj:i.id)                      ///
prior({subj:i.id},      normal(0, 1))                             ///
prior({discrim:i.item}, lognormal({mu_a}, {var_a}))               ///
prior({diff:i.item},    normal({mu_b}, {var_b}))                  ///
prior({gues:i.item},    igamma(10, 1))                            ///
prior({mu_a} {mu_b},    normal(0, 0.1))                           ///
prior({var_a} {var_b},  igamma(10, 1))                            ///
block({mu_a mu_b var_a var_b}, split)                             ///
init({discrim:i.item} 1 {gues:i.item} 0.1)                        ///
showreffects({discr:i.item} {diff:i.item} {gues:i.item})            ///
exclude({subj:i.id}) burnin(5000) saving(sim3pls, replace)        

bayesstats summary _all