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#!/usr/bin/env python |
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# -*- coding: utf-8 -*- |
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from __future__ import unicode_literals |
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from processors.utils import LabelManager |
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import networkx as nx |
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import collections |
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class DependencyUtils(object): |
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""" |
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A set of utilities for analyzing syntactic dependency graphs. |
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Methods |
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------- |
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build_networkx_graph(roots, edges, name) |
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Constructs a networkx.Graph |
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shortest_path(g, start, end) |
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Finds the shortest path in a `networkx.Graph` between any element in a list of start nodes and any element in a list of end nodes. |
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retrieve_edges(dep_graph, path) |
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Converts output of `shortest_path` into a list of triples that include the grammatical relation (and direction) for each node-node "hop" in the syntactic dependency graph. |
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simplify_tag(tag) |
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Maps part of speech (PoS) tag to a subset of PoS tags to better consolidate categorical labels. |
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lexicalize_path(sentence, path, words=False, lemmas=False, tags=False, simple_tags=False, entities=False) |
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Lexicalizes path in syntactic dependency graph using Odin-style token constraints. |
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pagerank(networkx_graph, alpha=0.85, personalization=None, max_iter=1000, tol=1e-06, nstart=None, weight='weight', dangling=None) |
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Measures node activity in a `networkx.Graph` using a thin wrapper around `networkx` implementation of pagerank algorithm (see `networkx.algorithms.link_analysis.pagerank`). Use with `processors.ds.DirectedGraph.graph`. |
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""" |
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UNKNOWN = LabelManager.UNKNOWN |
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@staticmethod |
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def build_networkx_graph(roots, edges, name): |
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""" |
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Converts a `processors` dependency graph into a networkx graph |
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""" |
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G = nx.Graph() |
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graph_name = name |
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# store roots |
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G.graph["roots"] = roots |
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edges = [(edge.source, edge.destination, {"relation": edge.relation}) for edge in edges] |
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G.add_edges_from(edges) |
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return G |
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@staticmethod |
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def shortest_path(g, start, end): |
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""" |
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Find the shortest path between two nodes. |
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Parameters |
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---------- |
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start : int or [int] |
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A single token index or list of token indices serving as the start of the graph traversal. |
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end : int or [int] |
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A single token index or list of token indices serving as the end of the graph traversal. |
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""" |
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start = start if isinstance(start, collections.Iterable) else [start] |
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end = end if isinstance(end, collections.Iterable) else [end] |
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# node list -> edges (i.e., (source, dest) pairs) |
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def path_to_edges(g, path): |
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return [(path[i], path[i+1]) for i in range(len(path) - 1)] |
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shortest_paths = [] |
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for s in start: |
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for e in end: |
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try: |
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path = nx.algorithms.shortest_path(g, s, e) |
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shortest_paths.append(path_to_edges(g, path)) |
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# no path found... |
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except: |
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#print("No path found between '{}' and '{}'".format(s, e)) |
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continue |
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return None if len(shortest_paths) == 0 else min(shortest_paths, key=lambda x: len(x)) |
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@staticmethod |
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def retrieve_edges(dep_graph, path): |
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""" |
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Converts output of Converts output of `DependencyUtils.shortest_path` |
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into a list of triples that include the grammatical relation (and direction) |
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for each node-node "hop" in the syntactic dependency graph. |
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Parameters |
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---------- |
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dep_graph : processors.ds.DirectedGraph |
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The `DirectedGraph` used to retrieve the grammatical relations for each edge in the `path`. |
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path : [(int, int)] |
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A list of tuples representing the shortest path from A to B in `dep_graph`. |
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Returns |
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------- |
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[(int, str, int)] |
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the shortest path (`path`) enhanced with the directed grammatical relations |
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(ex. `>nsubj` for `predicate` to `subject` vs. `<nsubj` for `subject` to `predicate`). |
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""" |
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shortest_path = [] |
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for (s, d) in path: |
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# build dictionaries from incoming/outgoing |
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outgoing = dep_graph.outgoing[s] |
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outgoing = dict(outgoing) if len(outgoing) > 0 else dict() |
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incoming = dep_graph.incoming[s] |
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incoming = dict(incoming) if len(incoming) > 0 else dict() |
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relation = ">{}".format(outgoing[d]) if d in outgoing else "<{}".format(incoming[d]) |
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shortest_path.append((s, relation, d)) |
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return shortest_path |
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@staticmethod |
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def simplify_tag(tag): |
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""" |
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Maps part of speech (PoS) tag to a subset of PoS tags to better consolidate categorical labels. |
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Parameters |
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---------- |
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tag : str |
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The Penn-style PoS tag to be mapped to a simplified form. |
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Returns |
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------- |
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str |
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A simplified form of `tag`. In some cases, the returned form may be identical to `tag`. |
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""" |
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simple_tag = "\"{}\"".format(tag) |
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# collapse plurals |
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if tag.startswith("NNP"): |
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simple_tag = "/^NNP/" |
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# collapse plurals |
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elif tag.startswith("NN"): |
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simple_tag = "/^N/" |
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elif tag.startswith("VB"): |
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simple_tag = "/^V/" |
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# collapse comparative, superlatives, etc. |
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elif tag.startswith("JJ"): |
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simple_tag = "/^J/" |
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# collapse comparative, superlatives, etc. |
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elif tag.startswith("RB"): |
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simple_tag = "/^RB/" |
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# collapse possessive/non-possesive pronouns |
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elif tag.startswith("PRP"): |
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simple_tag = "/^PRP/" |
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# treat WH determiners as DT |
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elif tag == "WDT": |
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simple_tag = "/DT$/" |
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# treat DT the same as WDT |
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elif tag == "DT": |
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simple_tag = "/DT$/" |
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return simple_tag |
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@staticmethod |
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def lexicalize_path(sentence, |
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path, |
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words=False, |
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lemmas=False, |
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tags=False, |
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simple_tags=False, |
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entities=False): |
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""" |
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Lexicalizes path in syntactic dependency graph using Odin-style token constraints. Operates on output of `DependencyUtils.retrieve_edges` |
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Parameters |
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---------- |
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sentence : processors.ds.Sentence |
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The `Sentence` from which the `path` was found. Used to lexicalize the `path`. |
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words : bool |
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Whether or not to encode nodes in the `path` with a token constraint constructed from `Sentence.words` |
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lemmas : bool |
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Whether or not to encode nodes in the `path` with a token constraint constructed from `Sentence.lemmas` |
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tags : bool |
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Whether or not to encode nodes in the `path` with a token constraint constructed from `Sentence.tags` |
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simple_tags : bool |
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Whether or not to encode nodes in the `path` with a token constraint constructed from `DependencyUtils.simplify_tag` applied to `Sentence.tags` |
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entities : bool |
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Whether or not to encode nodes in the `path` with a token constraint constructed from `Sentence._entities` |
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Returns |
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------- |
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[str] |
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The lexicalized form of `path`, encoded according to the specified parameters. |
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""" |
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UNKNOWN = LabelManager.UNKNOWN |
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lexicalized_path = [] |
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relations = [] |
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nodes = [] |
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# gather edges and nodes |
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for edge in path: |
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relations.append(edge[1]) |
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nodes.append(edge[0]) |
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nodes.append(path[-1][-1]) |
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for (i, node) in enumerate(nodes): |
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# build token constraints |
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token_constraints = [] |
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# words |
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if words: |
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token_constraints.append("word=\"{}\"".format(sentence.words[node])) |
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# PoS tags |
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if tags and sentence.tags[node] != UNKNOWN: |
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token_constraints.append("tag=\"{}\"".format(sentence.tags[node])) |
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# lemmas |
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if lemmas and sentence.lemmas[node] != UNKNOWN: |
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token_constraints.append("lemma=\"{}\"".format(sentence.lemmas[node])) |
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# NE labels |
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if entities and sentence._entities[node] != UNKNOWN: |
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token_constraints.append("entity=\"{}\"".format(sentence.entity[node])) |
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# simple tags |
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if simple_tags and sentence.tags[node] != UNKNOWN: |
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token_constraints.append("tag={}".format(DependencyUtils.simplify_tag(sentence.tags[node]))) |
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# build node pattern |
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if len(token_constraints) > 0: |
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node_pattern = "[{}]".format(" & ".join(token_constraints)) |
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# store lexicalized representation of node |
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lexicalized_path.append(node_pattern) |
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# append next edge |
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if i < len(relations): |
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lexicalized_path.append(relations[i]) |
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return lexicalized_path |
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@staticmethod |
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def pagerank(networkx_graph, |
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alpha=0.85, |
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personalization=None, |
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max_iter=1000, |
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tol=1e-06, |
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nstart=None, |
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weight='weight', |
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dangling=None): |
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""" |
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Measures node activity in a `networkx.Graph` using a thin wrapper around `networkx` implementation of pagerank algorithm (see `networkx.algorithms.link_analysis.pagerank`). Use with `processors.ds.DirectedGraph.graph`. |
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Parameters |
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---------- |
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networkx_graph : networkx.Graph |
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Corresponds to `G` parameter of `networkx.algorithms.link_analysis.pagerank`. |
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See Also |
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-------- |
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Method parameters correspond to those of [`networkx.algorithms.link_analysis.pagerank`](https://networkx.github.io/documentation/development/reference/generated/networkx.algorithms.link_analysis.pagerank_alg.pagerank.html#networkx.algorithms.link_analysis.pagerank_alg.pagerank) |
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""" |
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return nx.algorithms.link_analysis.pagerank(G=networkx_graph, alpha=alpha, personalization=personalization, max_iter=max_iter, tol=tol, nstart=nstart, weight=weight, dangling=dangling) |
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