laywerrobot/lib/python3.6/site-packages/sklearn/linear_model/ransac.py

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2020-08-27 21:55:39 +02:00
# coding: utf-8
# Author: Johannes Schönberger
#
# License: BSD 3 clause
import numpy as np
import warnings
from ..base import BaseEstimator, MetaEstimatorMixin, RegressorMixin, clone
from ..utils import check_random_state, check_array, check_consistent_length
from ..utils.random import sample_without_replacement
from ..utils.validation import check_is_fitted
from .base import LinearRegression
from ..utils.validation import has_fit_parameter
_EPSILON = np.spacing(1)
def _dynamic_max_trials(n_inliers, n_samples, min_samples, probability):
"""Determine number trials such that at least one outlier-free subset is
sampled for the given inlier/outlier ratio.
Parameters
----------
n_inliers : int
Number of inliers in the data.
n_samples : int
Total number of samples in the data.
min_samples : int
Minimum number of samples chosen randomly from original data.
probability : float
Probability (confidence) that one outlier-free sample is generated.
Returns
-------
trials : int
Number of trials.
"""
inlier_ratio = n_inliers / float(n_samples)
nom = max(_EPSILON, 1 - probability)
denom = max(_EPSILON, 1 - inlier_ratio ** min_samples)
if nom == 1:
return 0
if denom == 1:
return float('inf')
return abs(float(np.ceil(np.log(nom) / np.log(denom))))
class RANSACRegressor(BaseEstimator, MetaEstimatorMixin, RegressorMixin):
"""RANSAC (RANdom SAmple Consensus) algorithm.
RANSAC is an iterative algorithm for the robust estimation of parameters
from a subset of inliers from the complete data set. More information can
be found in the general documentation of linear models.
A detailed description of the algorithm can be found in the documentation
of the ``linear_model`` sub-package.
Read more in the :ref:`User Guide <ransac_regression>`.
Parameters
----------
base_estimator : object, optional
Base estimator object which implements the following methods:
* `fit(X, y)`: Fit model to given training data and target values.
* `score(X, y)`: Returns the mean accuracy on the given test data,
which is used for the stop criterion defined by `stop_score`.
Additionally, the score is used to decide which of two equally
large consensus sets is chosen as the better one.
If `base_estimator` is None, then
``base_estimator=sklearn.linear_model.LinearRegression()`` is used for
target values of dtype float.
Note that the current implementation only supports regression
estimators.
min_samples : int (>= 1) or float ([0, 1]), optional
Minimum number of samples chosen randomly from original data. Treated
as an absolute number of samples for `min_samples >= 1`, treated as a
relative number `ceil(min_samples * X.shape[0]`) for
`min_samples < 1`. This is typically chosen as the minimal number of
samples necessary to estimate the given `base_estimator`. By default a
``sklearn.linear_model.LinearRegression()`` estimator is assumed and
`min_samples` is chosen as ``X.shape[1] + 1``.
residual_threshold : float, optional
Maximum residual for a data sample to be classified as an inlier.
By default the threshold is chosen as the MAD (median absolute
deviation) of the target values `y`.
is_data_valid : callable, optional
This function is called with the randomly selected data before the
model is fitted to it: `is_data_valid(X, y)`. If its return value is
False the current randomly chosen sub-sample is skipped.
is_model_valid : callable, optional
This function is called with the estimated model and the randomly
selected data: `is_model_valid(model, X, y)`. If its return value is
False the current randomly chosen sub-sample is skipped.
Rejecting samples with this function is computationally costlier than
with `is_data_valid`. `is_model_valid` should therefore only be used if
the estimated model is needed for making the rejection decision.
max_trials : int, optional
Maximum number of iterations for random sample selection.
max_skips : int, optional
Maximum number of iterations that can be skipped due to finding zero
inliers or invalid data defined by ``is_data_valid`` or invalid models
defined by ``is_model_valid``.
.. versionadded:: 0.19
stop_n_inliers : int, optional
Stop iteration if at least this number of inliers are found.
stop_score : float, optional
Stop iteration if score is greater equal than this threshold.
stop_probability : float in range [0, 1], optional
RANSAC iteration stops if at least one outlier-free set of the training
data is sampled in RANSAC. This requires to generate at least N
samples (iterations)::
N >= log(1 - probability) / log(1 - e**m)
where the probability (confidence) is typically set to high value such
as 0.99 (the default) and e is the current fraction of inliers w.r.t.
the total number of samples.
residual_metric : callable, optional
Metric to reduce the dimensionality of the residuals to 1 for
multi-dimensional target values ``y.shape[1] > 1``. By default the sum
of absolute differences is used::
lambda dy: np.sum(np.abs(dy), axis=1)
.. deprecated:: 0.18
``residual_metric`` is deprecated from 0.18 and will be removed in
0.20. Use ``loss`` instead.
loss : string, callable, optional, default "absolute_loss"
String inputs, "absolute_loss" and "squared_loss" are supported which
find the absolute loss and squared loss per sample
respectively.
If ``loss`` is a callable, then it should be a function that takes
two arrays as inputs, the true and predicted value and returns a 1-D
array with the i-th value of the array corresponding to the loss
on ``X[i]``.
If the loss on a sample is greater than the ``residual_threshold``,
then this sample is classified as an outlier.
random_state : int, RandomState instance or None, optional, default None
The generator used to initialize the centers. If int, random_state is
the seed used by the random number generator; If RandomState instance,
random_state is the random number generator; If None, the random number
generator is the RandomState instance used by `np.random`.
Attributes
----------
estimator_ : object
Best fitted model (copy of the `base_estimator` object).
n_trials_ : int
Number of random selection trials until one of the stop criteria is
met. It is always ``<= max_trials``.
inlier_mask_ : bool array of shape [n_samples]
Boolean mask of inliers classified as ``True``.
n_skips_no_inliers_ : int
Number of iterations skipped due to finding zero inliers.
.. versionadded:: 0.19
n_skips_invalid_data_ : int
Number of iterations skipped due to invalid data defined by
``is_data_valid``.
.. versionadded:: 0.19
n_skips_invalid_model_ : int
Number of iterations skipped due to an invalid model defined by
``is_model_valid``.
.. versionadded:: 0.19
References
----------
.. [1] https://en.wikipedia.org/wiki/RANSAC
.. [2] http://www.cs.columbia.edu/~belhumeur/courses/compPhoto/ransac.pdf
.. [3] http://www.bmva.org/bmvc/2009/Papers/Paper355/Paper355.pdf
"""
def __init__(self, base_estimator=None, min_samples=None,
residual_threshold=None, is_data_valid=None,
is_model_valid=None, max_trials=100, max_skips=np.inf,
stop_n_inliers=np.inf, stop_score=np.inf,
stop_probability=0.99, residual_metric=None,
loss='absolute_loss', random_state=None):
self.base_estimator = base_estimator
self.min_samples = min_samples
self.residual_threshold = residual_threshold
self.is_data_valid = is_data_valid
self.is_model_valid = is_model_valid
self.max_trials = max_trials
self.max_skips = max_skips
self.stop_n_inliers = stop_n_inliers
self.stop_score = stop_score
self.stop_probability = stop_probability
self.residual_metric = residual_metric
self.random_state = random_state
self.loss = loss
def fit(self, X, y, sample_weight=None):
"""Fit estimator using RANSAC algorithm.
Parameters
----------
X : array-like or sparse matrix, shape [n_samples, n_features]
Training data.
y : array-like, shape = [n_samples] or [n_samples, n_targets]
Target values.
sample_weight : array-like, shape = [n_samples]
Individual weights for each sample
raises error if sample_weight is passed and base_estimator
fit method does not support it.
Raises
------
ValueError
If no valid consensus set could be found. This occurs if
`is_data_valid` and `is_model_valid` return False for all
`max_trials` randomly chosen sub-samples.
"""
X = check_array(X, accept_sparse='csr')
y = check_array(y, ensure_2d=False)
check_consistent_length(X, y)
if self.base_estimator is not None:
base_estimator = clone(self.base_estimator)
else:
base_estimator = LinearRegression()
if self.min_samples is None:
# assume linear model by default
min_samples = X.shape[1] + 1
elif 0 < self.min_samples < 1:
min_samples = np.ceil(self.min_samples * X.shape[0])
elif self.min_samples >= 1:
if self.min_samples % 1 != 0:
raise ValueError("Absolute number of samples must be an "
"integer value.")
min_samples = self.min_samples
else:
raise ValueError("Value for `min_samples` must be scalar and "
"positive.")
if min_samples > X.shape[0]:
raise ValueError("`min_samples` may not be larger than number "
"of samples ``X.shape[0]``.")
if self.stop_probability < 0 or self.stop_probability > 1:
raise ValueError("`stop_probability` must be in range [0, 1].")
if self.residual_threshold is None:
# MAD (median absolute deviation)
residual_threshold = np.median(np.abs(y - np.median(y)))
else:
residual_threshold = self.residual_threshold
if self.residual_metric is not None:
warnings.warn(
"'residual_metric' was deprecated in version 0.18 and "
"will be removed in version 0.20. Use 'loss' instead.",
DeprecationWarning)
if self.loss == "absolute_loss":
if y.ndim == 1:
loss_function = lambda y_true, y_pred: np.abs(y_true - y_pred)
else:
loss_function = lambda \
y_true, y_pred: np.sum(np.abs(y_true - y_pred), axis=1)
elif self.loss == "squared_loss":
if y.ndim == 1:
loss_function = lambda y_true, y_pred: (y_true - y_pred) ** 2
else:
loss_function = lambda \
y_true, y_pred: np.sum((y_true - y_pred) ** 2, axis=1)
elif callable(self.loss):
loss_function = self.loss
else:
raise ValueError(
"loss should be 'absolute_loss', 'squared_loss' or a callable."
"Got %s. " % self.loss)
random_state = check_random_state(self.random_state)
try: # Not all estimator accept a random_state
base_estimator.set_params(random_state=random_state)
except ValueError:
pass
estimator_fit_has_sample_weight = has_fit_parameter(base_estimator,
"sample_weight")
estimator_name = type(base_estimator).__name__
if (sample_weight is not None and not
estimator_fit_has_sample_weight):
raise ValueError("%s does not support sample_weight. Samples"
" weights are only used for the calibration"
" itself." % estimator_name)
if sample_weight is not None:
sample_weight = np.asarray(sample_weight)
n_inliers_best = 1
score_best = -np.inf
inlier_mask_best = None
X_inlier_best = None
y_inlier_best = None
self.n_skips_no_inliers_ = 0
self.n_skips_invalid_data_ = 0
self.n_skips_invalid_model_ = 0
# number of data samples
n_samples = X.shape[0]
sample_idxs = np.arange(n_samples)
n_samples, _ = X.shape
self.n_trials_ = 0
max_trials = self.max_trials
while self.n_trials_ < max_trials:
self.n_trials_ += 1
if (self.n_skips_no_inliers_ + self.n_skips_invalid_data_ +
self.n_skips_invalid_model_) > self.max_skips:
break
# choose random sample set
subset_idxs = sample_without_replacement(n_samples, min_samples,
random_state=random_state)
X_subset = X[subset_idxs]
y_subset = y[subset_idxs]
# check if random sample set is valid
if (self.is_data_valid is not None
and not self.is_data_valid(X_subset, y_subset)):
self.n_skips_invalid_data_ += 1
continue
# fit model for current random sample set
if sample_weight is None:
base_estimator.fit(X_subset, y_subset)
else:
base_estimator.fit(X_subset, y_subset,
sample_weight=sample_weight[subset_idxs])
# check if estimated model is valid
if (self.is_model_valid is not None and not
self.is_model_valid(base_estimator, X_subset, y_subset)):
self.n_skips_invalid_model_ += 1
continue
# residuals of all data for current random sample model
y_pred = base_estimator.predict(X)
# XXX: Deprecation: Remove this if block in 0.20
if self.residual_metric is not None:
diff = y_pred - y
if diff.ndim == 1:
diff = diff.reshape(-1, 1)
residuals_subset = self.residual_metric(diff)
else:
residuals_subset = loss_function(y, y_pred)
# classify data into inliers and outliers
inlier_mask_subset = residuals_subset < residual_threshold
n_inliers_subset = np.sum(inlier_mask_subset)
# less inliers -> skip current random sample
if n_inliers_subset < n_inliers_best:
self.n_skips_no_inliers_ += 1
continue
# extract inlier data set
inlier_idxs_subset = sample_idxs[inlier_mask_subset]
X_inlier_subset = X[inlier_idxs_subset]
y_inlier_subset = y[inlier_idxs_subset]
# score of inlier data set
score_subset = base_estimator.score(X_inlier_subset,
y_inlier_subset)
# same number of inliers but worse score -> skip current random
# sample
if (n_inliers_subset == n_inliers_best
and score_subset < score_best):
continue
# save current random sample as best sample
n_inliers_best = n_inliers_subset
score_best = score_subset
inlier_mask_best = inlier_mask_subset
X_inlier_best = X_inlier_subset
y_inlier_best = y_inlier_subset
max_trials = min(
max_trials,
_dynamic_max_trials(n_inliers_best, n_samples,
min_samples, self.stop_probability))
# break if sufficient number of inliers or score is reached
if n_inliers_best >= self.stop_n_inliers or \
score_best >= self.stop_score:
break
# if none of the iterations met the required criteria
if inlier_mask_best is None:
if ((self.n_skips_no_inliers_ + self.n_skips_invalid_data_ +
self.n_skips_invalid_model_) > self.max_skips):
raise ValueError(
"RANSAC skipped more iterations than `max_skips` without"
" finding a valid consensus set. Iterations were skipped"
" because each randomly chosen sub-sample failed the"
" passing criteria. See estimator attributes for"
" diagnostics (n_skips*).")
else:
raise ValueError(
"RANSAC could not find a valid consensus set. All"
" `max_trials` iterations were skipped because each"
" randomly chosen sub-sample failed the passing criteria."
" See estimator attributes for diagnostics (n_skips*).")
else:
if (self.n_skips_no_inliers_ + self.n_skips_invalid_data_ +
self.n_skips_invalid_model_) > self.max_skips:
warnings.warn("RANSAC found a valid consensus set but exited"
" early due to skipping more iterations than"
" `max_skips`. See estimator attributes for"
" diagnostics (n_skips*).",
UserWarning)
# estimate final model using all inliers
base_estimator.fit(X_inlier_best, y_inlier_best)
self.estimator_ = base_estimator
self.inlier_mask_ = inlier_mask_best
return self
def predict(self, X):
"""Predict using the estimated model.
This is a wrapper for `estimator_.predict(X)`.
Parameters
----------
X : numpy array of shape [n_samples, n_features]
Returns
-------
y : array, shape = [n_samples] or [n_samples, n_targets]
Returns predicted values.
"""
check_is_fitted(self, 'estimator_')
return self.estimator_.predict(X)
def score(self, X, y):
"""Returns the score of the prediction.
This is a wrapper for `estimator_.score(X, y)`.
Parameters
----------
X : numpy array or sparse matrix of shape [n_samples, n_features]
Training data.
y : array, shape = [n_samples] or [n_samples, n_targets]
Target values.
Returns
-------
z : float
Score of the prediction.
"""
check_is_fitted(self, 'estimator_')
return self.estimator_.score(X, y)