readCelIntensities <- function(filenames, indices = NULL, ..., verbose = 0){
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     # Validate arguments
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     # Argument 'filenames':
     if (length(filenames) == 0)
       stop("Argument 'filenames' is empty.");
     # Expand '~' pathnames to full pathnames.
     filenames <- file.path(dirname(filenames), basename(filenames));
     missing <- !file.exists(filenames);
     if(any(missing)) {
       missing <- paste(filenames[missing], collapse=", ");
       stop("Cannot read CEL files. Some files not found: ", missing);
     }
 
     # Argument 'verbose':
     if (length(verbose) != 1) {
       stop("Argument 'verbose' must be a single integer.");
     }
     if (!is.finite(as.integer(verbose))) {
       stop("Argument 'verbose' must be an integer: ", verbose);
     }
     verbose <- as.integer(verbose);
 
 
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     # Setup
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     if(verbose > 0) {
       cat("Entering readCelIntensities()\n ... reading headers\n");
     }
 
     # Read all CEL headers
     all.headers <- lapply(as.list(filenames), readCelHeader)
 
     # Validate that all chips are of the same type and have the same layout
     chiptype <- unique(sapply(all.headers, function(x) x$chiptype))
     if(length(chiptype) != 1) {
       warning("The CEL files do not have the same chiptype.")
     }
     nrows <- unique(sapply(all.headers, function(x) x$rows))
     ncols <- unique(sapply(all.headers, function(x) x$cols))
     if(length(nrows) != 1 || length(ncols) != 1) {
       stop("The CEL files dimension do not match.");
     }
 
     nfiles <- length(filenames);
     if(verbose > 0) {
       cat(" ...allocating memory for intensity matrix\n");
     }
 
     # Allocating return matrix
     if(is.null(indices)) {

       intensities <- matrix(NA_real_, nrow = nrows * ncols, ncol = nfiles)

     } else {

       intensities <- matrix(NA_real_, nrow = length(indices), ncol = nfiles)

     }
     colnames(intensities) <- filenames
 
 
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     # Reading intensities from all CEL files
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

     for (i in seq_len(nfiles)) {

       if(verbose > 0)
         cat(" ... reading", filenames[i], "\n");
 
       intensities[, i] <- readCel(filename = filenames[i],
                                   indices = indices,
                                   readIntensities = TRUE,
                                   readHeader = FALSE,
                                   readStdvs = FALSE,
                                   readPixels = FALSE,
                                   readXY = FALSE,
                                   readOutliers = FALSE,
                                   readMasked = FALSE,
                                   ...,
                                   verbose = (verbose - 1))$intensities
     } # for (i in ...)
 
     intensities;
 } # readCelIntensities()