nltk.DependencyEvaluator¶

class nltk.DependencyEvaluator(parsed_sents, gold_sents)[source]¶

Class for measuring labelled and unlabelled attachment score for dependency parsing. Note that the evaluation ignores punctuation.

>>> from nltk.parse import DependencyGraph, DependencyEvaluator

>>> gold_sent = DependencyGraph("""
... Pierre  NNP     2       NMOD
... Vinken  NNP     8       SUB
... ,       ,       2       P
... 61      CD      5       NMOD
... years   NNS     6       AMOD
... old     JJ      2       NMOD
... ,       ,       2       P
... will    MD      0       ROOT
... join    VB      8       VC
... the     DT      11      NMOD
... board   NN      9       OBJ
... as      IN      9       VMOD
... a       DT      15      NMOD
... nonexecutive    JJ      15      NMOD
... director        NN      12      PMOD
... Nov.    NNP     9       VMOD
... 29      CD      16      NMOD
... .       .       9       VMOD
... """)

>>> parsed_sent = DependencyGraph("""
... Pierre  NNP     8       NMOD
... Vinken  NNP     1       SUB
... ,       ,       3       P
... 61      CD      6       NMOD
... years   NNS     6       AMOD
... old     JJ      2       NMOD
... ,       ,       3       AMOD
... will    MD      0       ROOT
... join    VB      8       VC
... the     DT      11      AMOD
... board   NN      9       OBJECT
... as      IN      9       NMOD
... a       DT      15      NMOD
... nonexecutive    JJ      15      NMOD
... director        NN      12      PMOD
... Nov.    NNP     9       VMOD
... 29      CD      16      NMOD
... .       .       9       VMOD
... """)

>>> de = DependencyEvaluator([parsed_sent],[gold_sent])
>>> las, uas = de.eval()
>>> las
0.8...
>>> abs(uas - 0.6) < 0.00001
True