conv_ function(model, theta.idx = 0, error.idx = 0)
{
    if (is.null(model$Gibbs.iter))
        stop("\nmodel input not from gibbs(...) with opt=1")
    Gibbs_ model$Gibbs.iter
    iterations_ c(1:length(model$Gibbs.iter$thit[,1]))
    ix1_ theta.idx[theta.idx > 0 & theta.idx <= length(Gibbs$thit[1,])]
    ix2_ error.idx[error.idx > 0 & error.idx <= length(Gibbs$hit[1,])]
    if ( length(ix1) != 0 || length(ix2) !=0) {
        par(mfrow=c(3,2))
        for (i in 1:(length(ix1) + length(ix2))) {
            if (i != 1 && (i-1) %% 6 == 0) {
                cat("continue plotting (y/n) ?\t")
                ans_ scan(what = character(),n=1) 
                if (ans != "Y" && ans != "y" &&
                    ans != "Yes" && ans != "yes") stop()
                par(mfrow=c(3,2),ask = F)
            }
            if (i <= length(ix1)) {
                plot(iterations,Gibbs$thit[,ix1[i]],xlab="iterations",
                        ylab=paste("theta", ix1[i]),type="l",lty=1)
            }
            else {
                plot(iterations,Gibbs$hit[,ix2[i-length(ix1)]],
                    xlab="iterations", 
                    ylab=paste("err.pr", ix2[i-length(ix1)]),type="n")
                points(iterations,Gibbs$hit[,ix2[i-length(ix1)]],
                                                       type="l",lty=2)
            }
        } 	
    }
}