R/regmixEMlambdainit.R

In mixtools: Tools for Analyzing Finite Mixture Models

regmix.lambda.init = function (y, x, lambda = NULL, beta = NULL, s = NULL, k = 2, 
    addintercept = TRUE, arbmean = TRUE, arbvar = TRUE) 
{
    x <- as.matrix(x)
    n <- length(y)
    p <- ncol(x)
    if (addintercept) {
        x = x[, -1]
    }
    else x = x
    w = cbind(y, x)
    w = w[order(w[, 1]), ]
    w.bin = list()
    for (j in 1:k) {
        w.bin[[j]] <- w[max(1, floor((j - 1) * n/k)):ceiling(j * 
            n/k), ]
    }
    if (addintercept) {
        lm.out <- lapply(1:k, function(i) lm(w.bin[[i]][, 1] ~ 
            w.bin[[i]][, 2:p]))
    }
    else lm.out <- lapply(1:k, function(i) lm(w.bin[[i]][, 1] ~ 
        w.bin[[i]][, 2:(p + 1)] - 1))
    if (is.null(s)) {
        s.hyp = lapply(lm.out, anova)
        s.hyp = as.vector(sqrt(sapply(1:k, function(i) s.hyp[[i]]$Mean[length(s.hyp[[i]]$Mean)])))
        if (arbvar) {
            s = 1/rexp(k, rate = s.hyp)
        }
        else {
            s.hyp = mean(s.hyp)
            s = 1/rexp(1, rate = s.hyp)
        }
    }
    if (is.null(s) == FALSE && arbvar == TRUE) {
        k = length(s)
    }
    if (is.null(beta)) {
        beta.hyp = matrix(sapply(lm.out, coef), ncol = k)
        beta = matrix(0, nrow = p, ncol = k)
        for (j in 1:k) {
            beta[, j] = rnorm(p, mean = as.vector(beta.hyp[, 
                j]), sd = s[arbvar * j + (1 - arbvar)])
        }
        if (arbmean == FALSE) {
            beta = apply(beta, 1, mean)
        }
    }
    if (is.null(beta) == FALSE && arbmean == TRUE) {
        k = ncol(beta)
    }
    if (is.null(lambda)) {
        lam = runif(k)
        lam = lam/sum(lam)
	for(i in 1:n) {lambda <- rbind(lambda,lam)}
    }
    else k = ncol(lambda)
    list(lambda = lambda, beta = beta, s = s, k = k)
}