R/getUnivJ.R

In mpierrejean/jointSeg: Joint Segmentation of Multivariate (Copy Number) Signals

#' Get the contribution of one dimension to the RSE.
#' 
#' Get the contribution of one dimension to the Residual Squared Error (RSE)
#' 
#' This function is used internally by \code{\link{pruneByDP}}.
#' 
#' @param y Input vector of signals for the considered dimension
#' @param candCP A vector of candidate change points
#' @author Morgane Pierre-Jean and Pierre Neuvial
#' @seealso \code{\link{pruneByDP}}
#' @keywords internal
getUnivJ <- function(y, candCP) {
    isNotNA <- !is.na(y)
    idxsR <- c(0, cumsum(isNotNA))  ## index of original data in result
    ## idxsR <- idxsR[-length(idxsR)]

    ww <- which(isNotNA)
    y <- y[ww]
    n <- length(y)
    
    ## Compute boundaries of the smallest intervals considered
    cand <- sort(c(0, idxsR[1+candCP], n))
    k <- length(candCP) + 1 # number of intervals  

    S <- c(0, cumsum(y))
    V <- c(0, cumsum(y^2))

    JJ <- matrix(numeric(k*k), ncol=k)
    for (ii in 1:k) {
        Istart <- cand[ii] +1
        idxs <- seq(from=ii, to=k)
        Iend <- cand[idxs+1]
        JJ[ii, idxs] <- V[Iend+1] - V[Istart] - (S[Iend+1] - S[Istart])^2/(Iend-Istart+1)
    }
    return(JJ)
}

############################################################################
## HISTORY:
## 2013-01-30
## o Now an internal function (not exported anymore).
## 2012-12-XX
## o Created.
############################################################################