R/dotProdMatrix.R

In adductomicsR: Processing of adductomic mass spectral datasets

#' dot product matrix calculation
#' @param allSpectra a numeric matrix consisting of two columns
#' 1. mass and 2. intensity
#' @param spectraNames character names of individual spectra to compare
#' must equal number of rows of allSpectra
#' @param binSizeMS2 numeric the MS2 bin size to bin MS2 data prior
#' to dot product calculation (default = 0.1 Da).
#' @usage dotProdMatrix(allSpectra = NULL, spectraNames = NULL, binSizeMS2 =
#' NULL)
#' @return a matrix of equal dimension corresponding to the
#' number of unique spectrum names

dotProdMatrix <- function(allSpectra = NULL,
                            spectraNames = NULL,
                            binSizeMS2 = NULL) {
    # error handling
    stopifnot(is.matrix(allSpectra))
    stopifnot(is.character(spectraNames))
    message("Calculating dot product matrix ",
            length(unique(spectraNames)),
            " spectra\n")
    maxMass <- floor(max(allSpectra[, 1])) + 10
    # padded integer labels
    labelsTmp <-
        paste0("(",
                seq(binSizeMS2, (maxMass - binSizeMS2),
                    binSizeMS2),
                ",",
                seq((2 * binSizeMS2), maxMass, binSizeMS2),
                "]")
    massBinsIndivTmp <-
        cut(
            allSpectra[, 1],
            breaks = seq(binSizeMS2, maxMass,
                        binSizeMS2),
            labels = labelsTmp
        )
    # empty bins
    indivSpecVec <- tapply(allSpectra[, 2], paste0(spectraNames,
                                                    massBinsIndivTmp), sum)
    # identify any absent bins
    allBinNames <-
        paste0(rep(unique(spectraNames), each = length(labelsTmp)),
                rep(labelsTmp,
                    length(unique(spectraNames))))
    # add absent bins as zeros
    allBinsTmp <- rep(0, length(allBinNames))
    names(allBinsTmp) <- allBinNames
    # ensure indivSpecVec is in right order
    allBinsTmp[match(names(indivSpecVec), allBinNames)] <-
        indivSpecVec
    indivSpecMat <-
        matrix(allBinsTmp, byrow = FALSE, nrow = length(labelsTmp))
    # mean all pairwise dotproducts
    dotProdMat <- crossprod(indivSpecMat)
    sqrtMatrixTmp <- matrix(
        sqrt(colSums(indivSpecMat ^ 2)),
        nrow = nrow(dotProdMat),
        ncol = ncol(dotProdMat),
        byrow = TRUE
    )
    dotProdsTmp <- dotProdMat / (sqrtMatrixTmp * diag(sqrtMatrixTmp))
    row.names(dotProdsTmp) <- unique(spectraNames)
    colnames(dotProdsTmp) <- unique(spectraNames)
    return(dotProdsTmp)
}  # end function