spaCy/website/docs/usage/training.jade

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include ../../_includes/_mixins
p
| This tutorial describes how to train new statistical models for spaCy's
| part-of-speech tagger, named entity recognizer and dependency parser.
p
| I'll start with some quick code examples, that describe how to train
| each model. I'll then provide a bit of background about the algorithms,
| and explain how the data and feature templates work.
+h(2, "train-pos-tagger") Training the part-of-speech tagger
+code.
from spacy.vocab import Vocab
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from spacy.tagger import Tagger
from spacy.tokens import Doc
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from spacy.gold import GoldParse
vocab = Vocab(tag_map={'N': {'pos': 'NOUN'}, 'V': {'pos': 'VERB'}})
tagger = Tagger(vocab)
doc = Doc(vocab, words=['I', 'like', 'stuff'])
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gold = GoldParse(doc, tags=['N', 'V', 'N'])
tagger.update(doc, gold)
tagger.model.end_training()
p
+button(gh("spaCy", "examples/training/train_tagger.py"), false, "secondary") Full example
+h(2, "train-entity") Training the named entity recognizer
+code.
from spacy.vocab import Vocab
from spacy.pipeline import EntityRecognizer
from spacy.tokens import Doc
vocab = Vocab()
entity = EntityRecognizer(vocab, entity_types=['PERSON', 'LOC'])
doc = Doc(vocab, words=['Who', 'is', 'Shaka', 'Khan', '?'])
entity.update(doc, ['O', 'O', 'B-PERSON', 'L-PERSON', 'O'])
entity.model.end_training()
p
+button(gh("spaCy", "examples/training/train_ner.py"), false, "secondary") Full example
+h(2, "train-entity") Training the dependency parser
+code.
from spacy.vocab import Vocab
from spacy.pipeline import DependencyParser
from spacy.tokens import Doc
vocab = Vocab()
parser = DependencyParser(vocab, labels=['nsubj', 'compound', 'dobj', 'punct'])
doc = Doc(vocab, words=['Who', 'is', 'Shaka', 'Khan', '?'])
parser.update(doc, [(1, 'nsubj'), (1, 'ROOT'), (3, 'compound'), (1, 'dobj'),
(1, 'punct')])
parser.model.end_training()
p
+button(gh("spaCy", "examples/training/train_parser.py"), false, "secondary") Full example
+h(2, 'feature-templates') Customizing the feature extraction
p
| spaCy currently uses linear models for the tagger, parser and entity
| recognizer, with weights learned using the
| #[+a("https://explosion.ai/blog/part-of-speech-pos-tagger-in-python") Averaged Perceptron algorithm].
+aside("Linear Model Feature Scheme")
| For a list of the available feature atoms, see the #[+a("/docs/api/features") Linear Model Feature Scheme].
p
| Because it's a linear model, it's important for accuracy to build
| conjunction features out of the atomic predictors. Let's say you have
| two atomic predictors asking, "What is the part-of-speech of the
| previous token?", and "What is the part-of-speech of the previous
| previous token?". These ppredictors will introduce a number of features,
| e.g. #[code Prev-pos=NN], #[code Prev-pos=VBZ], etc. A conjunction
| template introduces features such as #[code Prev-pos=NN&Prev-pos=VBZ].
p
| The feature extraction proceeds in two passes. In the first pass, we
| fill an array with the values of all of the atomic predictors. In the
| second pass, we iterate over the feature templates, and fill a small
| temporary array with the predictors that will be combined into a
| conjunction feature. Finally, we hash this array into a 64-bit integer,
| using the MurmurHash algorithm. You can see this at work in the
| #[+a(gh("thinc", "thinc/linear/features.pyx", "94dbe06fd3c8f24d86ab0f5c7984e52dbfcdc6cb")) #[code thinc.linear.features]] module.
p
| It's very easy to change the feature templates, to create novel
| combinations of the existing atomic predictors. There's currently no API
| available to add new atomic predictors, though. You'll have to create a
| subclass of the model, and write your own #[code set_featuresC] method.
p
| The feature templates are passed in using the #[code features] keyword
| argument to the constructors of the #[+api("tagger") #[code Tagger]],
| #[+api("dependencyparser") #[code DependencyParser]] and
| #[+api("entityrecognizer") #[code EntityRecognizer]]:
+code.
from spacy.vocab import Vocab
from spacy.pipeline import Tagger
from spacy.tagger import P2_orth, P1_orth
from spacy.tagger import P2_cluster, P1_cluster, W_orth, N1_orth, N2_orth
vocab = Vocab(tag_map={'N': {'pos': 'NOUN'}, 'V': {'pos': 'VERB'}})
tagger = Tagger(vocab, features=[(P2_orth, P2_cluster), (P1_orth, P1_cluster),
(P2_orth,), (P1_orth,), (W_orth,),
(N1_orth,), (N2_orth,)])
p
| Custom feature templates can be passed to the #[code DependencyParser]
| and #[code EntityRecognizer] as well, also using the #[code features]
| keyword argument of the constructor.