Hello, I have quite the same problem. I tried to fix a response time and response accuracy model. mod_r2jags <- function(){ for (p in 1:P) { for(i in 1:I) { #response accuracy RA[p,i] ~ dbern(prob[p,i]) logit(prob[p,i]) <- item_parameter[i,1]* (potent[p,1]-item_parameter[i,2]) #response time LN_RT[p,i] ~ dnorm(mu_RT[p,i], sig[i]) mu_RT[p,i] <- item_parameter[i,4]-potent[p,2] sig[i]<-(item_parameter[i,3])^2 } potent[p,1:2] ~ dmnorm(mu_potent[1:2],invCovMat[1:2,1:2]) } I have this error message : Error...