Find the second highest value in a vector

penultimax.r

penultimax = function(invector) {
   # If the vector starts off as only having 1 or 0 numbers, return NA
  if (length(invector) <= 1) {
    return(NA)
  }
  first.max = safe.max(invector)
   #Once we get the max, take it out of the vector and make newvector
  newvector = invector[!invector == first.max]
   #If newvector now has nothing in it, return NA
  if (length(newvector) == 0) {
    return(NA)
  }
   #Now we get the second highest number in the vector.
   #So long as it's there, we return that second highest number (the penultimax)
   #or else we just return NA
  second.max = safe.max(newvector)
  if (is.na(first.max) & is.na(second.max)) {
    return (NA) }
  else if (!is.na(first.max) & is.na(second.max)) {
    return (NA) }
  else if (!is.na(first.max) & !is.na(second.max)) {
    return (second.max)}
  }


safe.max = function(invector) {
  na.pct = sum(is.na(invector))/length(invector)
  if (na.pct == 1) {
    return(NA) }
  else {
    return(max(invector,na.rm=TRUE))
  }
}