R/getCommonListElements.R

In aroma.core: Core Methods and Classes Used by 'aroma.*' Packages Part of the Aroma Framework

getCommonListElements <- function(lst, ignoreEmpty=TRUE) {
  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  # 1. Scan list for common elements
  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  # Vector to store common elements
  common <- c()
  n <- length(lst)
  first <- TRUE
  for (kk in seq_len(n)) {
    value <- lst[[kk]]

    # Ignoring empty list elements or not?
    if (is.null(value)) {
      if (ignoreEmpty)
        next

      # We know for sure that the rest will be empty too
      common <- c()
      break
    }

    if (first) {
      common <- value
      first <- FALSE
    } else {
      common <- intersect(common, value)

      # Done?
      if (length(common) == 0)
        break
    }
  } # for (kk ...)

  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  # 2. Keep only common elements
  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  lst <- lapply(lst, FUN=function(ss) {
    keep <- (ss %in% common)
    ss[keep]
  })

  lst
} # getCommonListElements()