/**
* Computes a score factor for a simple term or a phrase.
*
* The default implementation is:
* return idfFreq(searcher.docFreq(term), searcher.maxDoc());
*
* input - the term in question or array of terms
* reader - reader the document collection being searched
* Returns a score factor for the term
*
* @param mixed $input
* @param Zend_Search_Lucene $reader
* @return a score factor for the term
*/
public function idf($input, $reader)
{
if (!is_array($input)) {
return $this->idfFreq($reader->docFreq($input), $reader->count());
} else {
$idf = 0.0;
foreach ($input as $term) {
$idf += $this->idfFreq($reader->docFreq($term), $reader->count());
}
return $idf;
}
}