输出结果
初步处理后的 X_train： (984, 474)
(0, 0) 31.19418104265403
(0, 78) 1.0
(0, 82) 1.0
(0, 366) 1.0
(0, 391) 1.0
(0, 435) 1.0
(0, 437) 1.0
(0, 473) 1.0
(1, 0) 31.19418104265403
(1, 73) 1.0
(1, 79) 1.0
(1, 296) 1.0
(1, 389) 1.0
(1, 397) 1.0
(1, 436) 1.0
(1, 446) 1.0
(2, 0) 31.19418104265403
(2, 78) 1.0
(2, 82) 1.0
(2, 366) 1.0
(2, 391) 1.0
(2, 435) 1.0
(2, 437) 1.0
(2, 473) 1.0
(3, 0) 32.0
: :
(980, 473) 1.0
(981, 0) 12.0
(981, 73) 1.0
(981, 81) 1.0
(981, 84) 1.0
(981, 390) 1.0
(981, 435) 1.0
(981, 436) 1.0
(981, 473) 1.0
(982, 0) 18.0
(982, 78) 1.0
(982, 81) 1.0
(982, 277) 1.0
(982, 390) 1.0
(982, 435) 1.0
(982, 437) 1.0
(982, 473) 1.0
(983, 0) 31.19418104265403
(983, 78) 1.0
(983, 82) 1.0
(983, 366) 1.0
(983, 391) 1.0
(983, 435) 1.0
(983, 436) 1.0
(983, 473) 1.0 经过FS处理后的 X_train_fs： (984, 94)
(0, 93) 1.0
(0, 85) 1.0
(0, 83) 1.0
(0, 76) 1.0
(0, 71) 1.0
(0, 27) 1.0
(0, 24) 1.0
(0, 0) 31.19418104265403
(1, 84) 1.0
(1, 74) 1.0
(1, 63) 1.0
(1, 25) 1.0
(1, 19) 1.0
(1, 0) 31.19418104265403
(2, 93) 1.0
(2, 85) 1.0
(2, 83) 1.0
(2, 76) 1.0
(2, 71) 1.0
(2, 27) 1.0
(2, 24) 1.0
(2, 0) 31.19418104265403
(3, 93) 1.0
(3, 85) 1.0
(3, 83) 1.0
: :
(980, 24) 1.0
(980, 0) 31.19418104265403
(981, 93) 1.0
(981, 84) 1.0
(981, 83) 1.0
(981, 75) 1.0
(981, 28) 1.0
(981, 26) 1.0
(981, 19) 1.0
(981, 0) 12.0
(982, 93) 1.0
(982, 85) 1.0
(982, 83) 1.0
(982, 75) 1.0
(982, 26) 1.0
(982, 24) 1.0
(982, 0) 18.0
(983, 93) 1.0
(983, 84) 1.0
(983, 83) 1.0
(983, 76) 1.0
(983, 71) 1.0
(983, 27) 1.0
(983, 24) 1.0
(983, 0) 31.19418104265403
设计思路
核心代码
class SelectPercentile Found at: sklearn.feature_selection.univariate_selection
class SelectPercentile(_BaseFilter):
"""Select features according to a percentile of the highest scores.
Read more in the :ref:`User Guide <univariate_feature_selection>`.
Parameters
----------
score_func : callable
Function taking two arrays X and y, and returning a pair of arrays
(scores, pvalues) or a single array with scores.
Default is f_classif (see below "See also"). The default function only
works with classification tasks.
percentile : int, optional, default=10
Percent of features to keep.
Attributes
----------
scores_ : array-like, shape=(n_features,)
Scores of features.
pvalues_ : array-like, shape=(n_features,)
p-values of feature scores, None if `score_func` returned only scores.
Notes
-----
Ties between features with equal scores will be broken in an unspecified
way.
See also
--------
f_classif: ANOVA F-value between label/feature for classification tasks.
mutual_info_classif: Mutual information for a discrete target.
chi2: Chi-squared stats of non-negative features for classification tasks.
f_regression: F-value between label/feature for regression tasks.
mutual_info_regression: Mutual information for a continuous target.
SelectKBest: Select features based on the k highest scores.
SelectFpr: Select features based on a false positive rate test.
SelectFdr: Select features based on an estimated false discovery rate.
SelectFwe: Select features based on family-wise error rate.
GenericUnivariateSelect: Univariate feature selector with configurable mode.
"""
def __init__(self, score_func=f_classif, percentile=10):
super(SelectPercentile, self).__init__(score_func)
self.percentile = percentile
def _check_params(self, X, y):
if not 0 <= self.percentile <= 100:
raise ValueError(
"percentile should be >=0, <=100; got %r" % self.percentile)
def _get_support_mask(self):
check_is_fitted(self, 'scores_')
# Cater for NaNs
if self.percentile == 100:
return np.ones(len(self.scores_), dtype=np.bool)
elif self.percentile == 0:
return np.zeros(len(self.scores_), dtype=np.bool)
scores = _clean_nans(self.scores_)
treshold = stats.scoreatpercentile(scores,
100 - self.percentile)
mask = scores > treshold
ties = np.where(scores == treshold)[0]
if len(ties):
max_feats = int(len(scores) * self.percentile / 100)
kept_ties = ties[:max_feats - mask.sum()]
mask[kept_ties] = True
return mask
