Check to see if an array element exists and returning a boolean.

isNone.R

newPointer=function(inputValue){     # see : http://www.stat.berkeley.edu/~paciorek/computingTips/Pointers_passing_reference_.html
  object=new.env(parent=globalenv())  
  object$value=inputValue  
  class(object)='pointer'
  return(object)  
}
exDb <- function(t,i,v = F){#Check if element i exists in t
  r = F
  tryCatch({
    temp <- newPointer(t[[i]])             # Attempt to access variable location in question
    if(is.null(temp$value)){r = F}else{r = T} #If the prior line of code passes without error it is assured that the value exists but is it null?
  }, error = function(e){
    if(v){print(paste('Warning:',e))}#Lets you know the error
    r = F                         #sets return value to False
  })
  return(r)
}