R/cov-miss-mix-wt.R

In hhsmm: Hidden Hybrid Markov/Semi-Markov Model Fitting

#' weighted covariance for data with missing values
#'
#' The weighted means and variances using the 
#' observation matrix and the estimated weight 
#' vectors for a data matrix containing missing values (NA or NaN)
#'
#' @author Morteza Amini, \email{morteza.amini@@ut.ac.ir}
#'
#' @param x the observation matrix, which can contain missing values (NA or NaN)
#' @param means a list containing the means of the missing values given observed values
#' @param secm a list containing the second moments of the missing values given observed values
#' @param wt1 the state probabilities matrix (number of observations 
#' times number of states)
#' @param wt2 the mixture components probabilities list (of length 
#' nstate) of matrices (number of observations times number of 
#' mixture components)
#' @param cor logical. if TRUE the weighted correlation is also given
#' @param center logical. if TRUE the weighted mean is also given
#' @param method with two possible entries:
#' \itemize{
#' \item \code{"unbiased"} the unbiased estimator is given
#' \item \code{"ML"} the maximum likelihood estimator is given
#' }
#'
#' @return list containing the following items:
#' \itemize{
#' \item \code{center} the weighted mean of \code{x}
#' \item \code{cov} the weighted covariance of \code{x}
#' \item \code{n.obs} the number of observations in \code{x}
#' \item \code{cor} the weighted correlation of \code{x}, 
#' if the parameter \code{cor} is TRUE
#' \item \code{wt1} the state weighs \code{wt1}
#' \item \code{wt2} the mixture component weights \code{wt2}
#' \item \code{pmix} the estimated mixture proportions
#' }
#'
#' @examples
#' data(CMAPSS)
#' x0 = CMAPSS$train$x[1:CMAPSS$train$N[1], ]
#' n = nrow(x0)
#' wt1 = runif(n)
#' wt2 = runif(n)
#' p = ncol(x0)
#' sammissall = sample(1:n, trunc(n / 20))
#' means = secm = list()
#' for(ii in 1:n){ 
#' 	if(ii %in% sammissall){
#'    means[[ii]] = colMeans(x0[sammissall, ])
#'    secm[[ii]] = t(x0[sammissall, ]) %*% x0[sammissall, ]
#'  }else{
#'	  means[[ii]] = secm[[ii]] = NA
#'  }
#' }
#' x0[sammissall,] = NA
#' 
#' cov.miss.mix.wt(x0, means, secm, wt1, wt2)
#' 
#' @export
#'
cov.miss.mix.wt <- function(x, means, secm, wt1 = rep(1/nrow(x), nrow(x)), 
	wt2 = rep(1/nrow(x), nrow(x)), cor = FALSE, center = TRUE, 
	method = c("unbiased", "ML"))
{
    if (is.data.frame(x)) 
        x <- as.matrix(x)
    else if (!is.matrix(x)) 
        stop("'x' must be a matrix or a data frame")
    if (!all(is.finite(x) | is.na(x)| is.nan(x))) 
        stop("'x' must contain finite values only")
    n <- nrow(x)
    if (length(wt1) != n || length(wt2) != n) 
        stop("length of 'wt's must equal the number of rows in 'x'")
    if (any(wt1 < 0) || any(wt2 < 0)) 
        stop("weights must be non-negative!")
    if ((s1 <- sum(wt1)) == 0) 
        stop("state weights must be not all zero")
    if ((s2 <- sum(wt2)) == 0) 
        warning("for some mixture components weights are all zero! 
			The components are not used!")
	wt <- wt1 * wt2 / sum(wt1 * wt2)
	xr = x
	for (i in 1:nrow(xr)) xr[i, is.na(xr[i, ]) | is.nan(xr[i, ])] = means[[i]]
    if (is.logical(center)) {
        center <- if (center){ 
            colSums(wt * xr) 
        } else 0
    } else {
        if (length(center) != ncol(x)) 
            stop("length of 'center' must equal the number of columns in 'x'")
    }
	cov1 = matrix(0, ncol(x), ncol(x))
	missed = apply(x, 1, function(t) which(is.na(t) | is.nan(t)))
	for (i in 1:nrow(x)){
		covtmp = crossprod(sqrt(wt[i]) * sweep(t(as.matrix(xr[i, ])), 
				2, center, check.margin = FALSE))
		if (length(missed[[i]]) > 0){
			covmm = wt[i] * (secm[[i]] + center[missed[[i]]] %*% 
				t(center[missed[[i]]]) - center[missed[[i]]] %*% 
				t(means[[i]]) - means[[i]] %*% t(center[missed[[i]]]))
			covtmp[missed[[i]], missed[[i]]] = covmm 
		}
		cov1 = cov1 + covtmp
	}
    cov <- switch(match.arg(method), unbiased = cov1/(1 - sum(wt^2)), 
			ML = cov1)
    	y <- list(cov = cov, center = center, n.obs = n)
    	y$wt1 <- wt1
    	y$wt2 <- wt2
	y$pmix = mean(wt2)
    if (cor){
        Is <- 1 / sqrt(diag(cov))
        R <- cov
        R[] <- Is * cov * rep(Is, each = nrow(cov))
        y$cor <- R
    }
    y
}