Here is a script that works for columns starting out with ASCII characters and gives '?' for non-ASCII characters:

# (TERR or R)

# NameDecode function definition
# Summary:
# NameDecode translate codes to characters.
# For coded ASCII and ISO 8859-1 Latin 1 characters this function decodes in the same way as
# the NameDecode expression method does in Spotfire. All other codes are translated to . .
#
# Codes look like ..xyz  where x, y and z are characters matching [0-9a-zA-Z].
#
# Parameter: str ; A character string
# Result:  A character string where all codes are replaced with the coded character
#
NameDecode <- function(str)
{
  byteToCharacter <- function(bytes)
  {
    c001.007 <- "\001\002\003\004\005\006\007";
    c010.077 <- "\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037\040\041\042\043\044\045\046\047\050\051\052\053\054\055\056\057\060\061\062\063\064\065\066\067\070\071\072\073\074\075\076\077";
    c100.107 <- "\100\101\102\103\104\105\106\107";
    c110.177 <- "\110\111\112\113\114\115\116\117\120\121\122\123\124\125\126\127\130\131\132\133\134\135\136\137\140\141\142\143\144\145\146\147\150\151\152\153\154\155\156\157\160\161\162\163\164\165\166\167\170\171\172\173\174\175\176\177";
    c200.207 <- "\200\201\202\203\204\205\206\207";
    c210.277 <- "\210\211\212\213\214\215\216\217\220\221\222\223\224\225\226\227\230\231\232\233\234\235\236\237\240\241\242\243\244\245\246\247\250\251\252\253\254\255\256\257\260\261\262\263\264\265\266\267\270\271\272\273\274\275\276\277";
    c300.307 <- "\300\301\302\303\304\305\306\307";
    c310.377 <- "\310\311\312\313\314\315\316\317\320\321\322\323\324\325\326\327\330\331\332\333\334\335\336\337\340\341\342\343\344\345\346\347\350\351\352\353\354\355\356\357\360\361\362\363\364\365\366\367\370\371\372\373\374\375\376\377";
    v.c001.377 <- unlist(strsplit(c(c001.007, c010.077, c100.107, c110.177, c200.207, c210.277, c300.307, c310.377), ""));
    v.c001.377[bytes]
  }
  NameDecode.OneCode <- function(str, byteToCharacter)
  {
    digits <- unlist(strsplit("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", ""));
    replace <- str;
    sv <- unlist(strsplit(str, ""));
    ib <- match(sv[3:5], digits) - 1;
    byte <- sum(ib * c(62 * 62, 62, 1));
    if (byte == 0)
    {
       replace <- str;
    }
    else if (byte < 256)
    {
      replace <- byteToCharacter(byte);
    }
    else if (byte < 65536)
    {
      # Here other coded UTF-16 characters is replaced with a .
      # Inside Spotfire they are decoded.
      replace <- ".";
    }
    else
    {
      replace <- str;
    }
  }

  codeLength = 5;
  rightStr <- str;
  decodedStr <- "";
  matchIndex <- regexpr("[.][.][0-9a-h][0-9a-zA-Z][0-9a-zA-Z]", rightStr);
  while (matchIndex > 0)
  {
    decodedStr <- paste(
      decodedStr,
      substring(rightStr, 1, matchIndex - 1),
      NameDecode.OneCode(substring(rightStr, matchIndex, matchIndex + codeLength - 1), byteToCharacter),
      sep="");
    rightStr <- substring(rightStr, matchIndex + codeLength, nchar(rightStr));
    matchIndex <- regexpr("[.][.][0-9a-h][0-9a-zA-Z][0-9a-zA-Z]", rightStr);            
  }
  decodedStr <- paste(decodedStr, rightStr, sep = "");
  decodedStr
}

#
# Example
#
names <- data.frame(encoded = names(input), decoded = sapply(names(input), FUN = NameDecode));