/**
* Returns an explanation for the normalized term frequency.
*
* <p>The default normalization methods use the field length of the document and the average field
* length to compute the normalized term frequency. This method provides a generic explanation for
* such methods. Subclasses that use other statistics must override this method.
*/
public Explanation explain(BasicStats stats, float tf, float len) {
Explanation result = new Explanation();
result.setDescription(getClass().getSimpleName() + ", computed from: ");
result.setValue(tfn(stats, tf, len));
result.addDetail(new Explanation(tf, "tf"));
result.addDetail(new Explanation(stats.getAvgFieldLength(), "avgFieldLength"));
result.addDetail(new Explanation(len, "len"));
return result;
}
