Source code for cornac.eval_methods.stratified_split

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from math import ceil
from collections import defaultdict

from .base_method import BaseMethod
from .ratio_split import RatioSplit
from ..utils import get_rng
from ..utils.common import safe_indexing


[docs]class StratifiedSplit(BaseMethod): """Grouping data by user or item then splitting data into training, validation, and test sets. Parameters ---------- data: array-like, required Raw preference data in the triplet format [(user_id, item_id, rating_value, timestamp)]. group_by: str, optional, default: 'user' Grouping by 'user' or 'item'. chrono: bool, optional, default False Data is ordered by reviewed time or not. If this option is True, data must be in 'UIRT' format. test_size: float, optional, default: 0.2 The proportion of the test set, \ if > 1 then it is treated as the size of the test set. val_size: float, optional, default: 0.0 The proportion of the validation set, \ if > 1 then it is treated as the size of the validation set. rating_threshold: float, optional, default: 1.0 Threshold used to binarize rating values into positive or negative feedback for model evaluation using ranking metrics (rating metrics are not affected). seed: int, optional, default: None Random seed for reproducibility. exclude_unknowns: bool, optional, default: True If `True`, unknown users and items will be ignored during model evaluation. verbose: bool, optional, default: False Output running log. """ def __init__( self, data, group_by="user", chrono=False, fmt="UIRT", test_size=0.2, val_size=0.0, rating_threshold=1.0, seed=None, exclude_unknowns=True, verbose=False, **kwargs ): super().__init__( data=data, fmt=fmt, rating_threshold=rating_threshold, seed=seed, exclude_unknowns=exclude_unknowns, verbose=verbose, **kwargs ) if group_by not in ["user", "item"]: raise ValueError( "group_by option must be either 'user' or 'item' but {}".format( group_by ) ) if chrono and (fmt != "UIRT" or len(self._data[0]) != 4): raise ValueError( 'Input data must be in "UIRT" format for sorting chronologically.' ) self.chrono = chrono self.group_by = group_by self.val_size = val_size self.test_size = test_size self._split() def _split(self): data = ( sorted(self._data, key=lambda x: x[3]) if self.chrono else self._data ) # sort data chronologically grouped_indices = defaultdict(list) for idx, (uid, iid, *_) in enumerate(data): if self.group_by == "user": grouped_indices[uid].append(idx) else: grouped_indices[iid].append(idx) train_idx = [] test_idx = [] val_idx = [] for rating_indices in grouped_indices.values(): n_ratings = len(rating_indices) n_train, _, n_test = RatioSplit.validate_size( self.val_size, self.test_size, n_ratings ) if self.chrono: # training portion is chronologically sorted # validation and test portions are randomly selected rating_indices = ( rating_indices[:n_train] + self.rng.permutation(rating_indices[n_train:]).tolist() ) else: rating_indices = self.rng.permutation(rating_indices).tolist() train_idx += rating_indices[:n_train] test_idx += rating_indices[-n_test:] val_idx += rating_indices[n_train:-n_test] train_data = safe_indexing(data, train_idx) test_data = safe_indexing(data, test_idx) val_data = safe_indexing(data, val_idx) if len(val_idx) > 0 else None self.build(train_data=train_data, test_data=test_data, val_data=val_data)