nltk.translate.metrics module

nltk.translate.metrics.alignment_error_rate(reference, hypothesis, possible=None)[source]

Return the Alignment Error Rate (AER) of an alignment with respect to a “gold standard” reference alignment. Return an error rate between 0.0 (perfect alignment) and 1.0 (no alignment).

>>> from nltk.translate import Alignment
>>> ref = Alignment([(0, 0), (1, 1), (2, 2)])
>>> test = Alignment([(0, 0), (1, 2), (2, 1)])
>>> alignment_error_rate(ref, test) 
0.6666666666666667
Parameters:

  • reference (Alignment) – A gold standard alignment (sure alignments)

  • hypothesis (Alignment) – A hypothesis alignment (aka. candidate alignments)

  • possible (Alignment or None) – A gold standard reference of possible alignments (defaults to reference if None)

Return type:

float or None