Idf Enumeration |
| Member name | Value | Description |
|---|---|---|
| Normalized | 0 | BM25 variant, idf = log((N-n+1)/n), as per Robertson et al where N is the collection size and n is the number of matched documents. |
| Plain | 1 | Plain variant, idf=log(N/n), as per Sparck-Jones where N is the collection size and n is the number of matched documents. |