"""Wrapper for using the Scikit-Learn API with Keras models.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import copy
import types
import numpy as np
from ..utils.np_utils import to_categorical
from ..utils.generic_utils import has_arg
from ..utils.generic_utils import to_list
from ..models import Sequential
class BaseWrapper(object):
"""Base class for the Keras scikit-learn wrapper.
Warning: This class should not be used directly.
Use descendant classes instead.
# Arguments
build_fn: callable function or class instance
**sk_params: model parameters & fitting parameters
The `build_fn` should construct, compile and return a Keras model, which
will then be used to fit/predict. One of the following
three values could be passed to `build_fn`:
1. A function
2. An instance of a class that implements the `__call__` method
3. None. This means you implement a class that inherits from either
`KerasClassifier` or `KerasRegressor`. The `__call__` method of the
present class will then be treated as the default `build_fn`.
`sk_params` takes both model parameters and fitting parameters. Legal model
parameters are the arguments of `build_fn`. Note that like all other
estimators in scikit-learn, `build_fn` should provide default values for
its arguments, so that you could create the estimator without passing any
values to `sk_params`.
`sk_params` could also accept parameters for calling `fit`, `predict`,
`predict_proba`, and `score` methods (e.g., `epochs`, `batch_size`).
fitting (predicting) parameters are selected in the following order:
1. Values passed to the dictionary arguments of
`fit`, `predict`, `predict_proba`, and `score` methods
2. Values passed to `sk_params`
3. The default values of the `keras.models.Sequential`
`fit`, `predict`, `predict_proba` and `score` methods
When using scikit-learn's `grid_search` API, legal tunable parameters are
those you could pass to `sk_params`, including fitting parameters.
In other words, you could use `grid_search` to search for the best
`batch_size` or `epochs` as well as the model parameters.
"""
def __init__(self, build_fn=None, **sk_params):
self.build_fn = build_fn
self.sk_params = sk_params
self.check_params(sk_params)
def check_params(self, params):
"""Checks for user typos in `params`.
# Arguments
params: dictionary; the parameters to be checked
# Raises
ValueError: if any member of `params` is not a valid argument.
"""
legal_params_fns = [Sequential.fit, Sequential.predict,
Sequential.predict_classes, Sequential.evaluate]
if self.build_fn is None:
legal_params_fns.append(self.__call__)
elif (not isinstance(self.build_fn, types.FunctionType) and
not isinstance(self.build_fn, types.MethodType)):
legal_params_fns.append(self.build_fn.__call__)
else:
legal_params_fns.append(self.build_fn)
for params_name in params:
for fn in legal_params_fns:
if has_arg(fn, params_name):
break
else:
if params_name != 'nb_epoch':
raise ValueError(
'{} is not a legal parameter'.format(params_name))
def get_params(self, **params):
"""Gets parameters for this estimator.
# Arguments
**params: ignored (exists for API compatibility).
# Returns
Dictionary of parameter names mapped to their values.
"""
res = copy.deepcopy(self.sk_params)
res.update({'build_fn': self.build_fn})
return res
def set_params(self, **params):
"""Sets the parameters of this estimator.
# Arguments
**params: Dictionary of parameter names mapped to their values.
# Returns
self
"""
self.check_params(params)
self.sk_params.update(params)
return self
def fit(self, x, y, **kwargs):
"""Constructs a new model with `build_fn` & fit the model to `(x, y)`.
# Arguments
x : array-like, shape `(n_samples, n_features)`
Training samples where `n_samples` is the number of samples
and `n_features` is the number of features.
y : array-like, shape `(n_samples,)` or `(n_samples, n_outputs)`
True labels for `x`.
**kwargs: dictionary arguments
Legal arguments are the arguments of `Sequential.fit`
# Returns
history : object
details about the training history at each epoch.
"""
if self.build_fn is None:
self.model = self.__call__(**self.filter_sk_params(self.__call__))
elif (not isinstance(self.build_fn, types.FunctionType) and
not isinstance(self.build_fn, types.MethodType)):
self.model = self.build_fn(
**self.filter_sk_params(self.build_fn.__call__))
else:
self.model = self.build_fn(**self.filter_sk_params(self.build_fn))
loss_name = self.model.loss
if hasattr(loss_name, '__name__'):
loss_name = loss_name.__name__
if loss_name == 'categorical_crossentropy' and len(y.shape) != 2:
y = to_categorical(y)
fit_args = copy.deepcopy(self.filter_sk_params(Sequential.fit))
fit_args.update(kwargs)
history = self.model.fit(x, y, **fit_args)
return history
def filter_sk_params(self, fn, override=None):
"""Filters `sk_params` and returns those in `fn`'s arguments.
# Arguments
fn : arbitrary function
override: dictionary, values to override `sk_params`
# Returns
res : dictionary containing variables
in both `sk_params` and `fn`'s arguments.
"""
override = override or {}
res = {}
for name, value in self.sk_params.items():
if has_arg(fn, name):
res.update({name: value})
res.update(override)
return res
class KerasClassifier(BaseWrapper):
"""Implementation of the scikit-learn classifier API for Keras.
"""
def fit(self, x, y, sample_weight=None, **kwargs):
"""Constructs a new model with `build_fn` & fit the model to `(x, y)`.
# Arguments
x : array-like, shape `(n_samples, n_features)`
Training samples where `n_samples` is the number of samples
and `n_features` is the number of features.
y : array-like, shape `(n_samples,)` or `(n_samples, n_outputs)`
True labels for `x`.
**kwargs: dictionary arguments
Legal arguments are the arguments of `Sequential.fit`
# Returns
history : object
details about the training history at each epoch.
# Raises
ValueError: In case of invalid shape for `y` argument.
"""
y = np.array(y)
if len(y.shape) == 2 and y.shape[1] > 1:
self.classes_ = np.arange(y.shape[1])
elif (len(y.shape) == 2 and y.shape[1] == 1) or len(y.shape) == 1:
self.classes_ = np.unique(y)
y = np.searchsorted(self.classes_, y)
else:
raise ValueError('Invalid shape for y: ' + str(y.shape))
self.n_classes_ = len(self.classes_)
if sample_weight is not None:
kwargs['sample_weight'] = sample_weight
return super(KerasClassifier, self).fit(x, y, **kwargs)
def predict(self, x, **kwargs):
"""Returns the class predictions for the given test data.
# Arguments
x: array-like, shape `(n_samples, n_features)`
Test samples where `n_samples` is the number of samples
and `n_features` is the number of features.
**kwargs: dictionary arguments
Legal arguments are the arguments
of `Sequential.predict_classes`.
# Returns
preds: array-like, shape `(n_samples,)`
Class predictions.
"""
kwargs = self.filter_sk_params(Sequential.predict_classes, kwargs)
proba = self.model.predict(x, **kwargs)
if proba.shape[-1] > 1:
classes = proba.argmax(axis=-1)
else:
classes = (proba > 0.5).astype('int32')
return self.classes_[classes]
def predict_proba(self, x, **kwargs):
"""Returns class probability estimates for the given test data.
# Arguments
x: array-like, shape `(n_samples, n_features)`
Test samples where `n_samples` is the number of samples
and `n_features` is the number of features.
**kwargs: dictionary arguments
Legal arguments are the arguments
of `Sequential.predict_classes`.
# Returns
proba: array-like, shape `(n_samples, n_outputs)`
Class probability estimates.
In the case of binary classification,
to match the scikit-learn API,
will return an array of shape `(n_samples, 2)`
(instead of `(n_sample, 1)` as in Keras).
"""
kwargs = self.filter_sk_params(Sequential.predict_proba, kwargs)
probs = self.model.predict(x, **kwargs)
# check if binary classification
if probs.shape[1] == 1:
# first column is probability of class 0 and second is of class 1
probs = np.hstack([1 - probs, probs])
return probs
def score(self, x, y, **kwargs):
"""Returns the mean accuracy on the given test data and labels.
# Arguments
x: array-like, shape `(n_samples, n_features)`
Test samples where `n_samples` is the number of samples
and `n_features` is the number of features.
y: array-like, shape `(n_samples,)` or `(n_samples, n_outputs)`
True labels for `x`.
**kwargs: dictionary arguments
Legal arguments are the arguments of `Sequential.evaluate`.
# Returns
score: float
Mean accuracy of predictions on `x` wrt. `y`.
# Raises
ValueError: If the underlying model isn't configured to
compute accuracy. You should pass `metrics=["accuracy"]` to
the `.compile()` method of the model.
"""
y = np.searchsorted(self.classes_, y)
kwargs = self.filter_sk_params(Sequential.evaluate, kwargs)
loss_name = self.model.loss
if hasattr(loss_name, '__name__'):
loss_name = loss_name.__name__
if loss_name == 'categorical_crossentropy' and len(y.shape) != 2:
y = to_categorical(y)
outputs = self.model.evaluate(x, y, **kwargs)
outputs = to_list(outputs)
for name, output in zip(self.model.metrics_names, outputs):
if name == 'acc':
return output
raise ValueError('The model is not configured to compute accuracy. '
'You should pass `metrics=["accuracy"]` to '
'the `model.compile()` method.')
class KerasRegressor(BaseWrapper):
"""Implementation of the scikit-learn regressor API for Keras.
"""
def predict(self, x, **kwargs):
"""Returns predictions for the given test data.
# Arguments
x: array-like, shape `(n_samples, n_features)`
Test samples where `n_samples` is the number of samples
and `n_features` is the number of features.
**kwargs: dictionary arguments
Legal arguments are the arguments of `Sequential.predict`.
# Returns
preds: array-like, shape `(n_samples,)`
Predictions.
"""
kwargs = self.filter_sk_params(Sequential.predict, kwargs)
return np.squeeze(self.model.predict(x, **kwargs))
def score(self, x, y, **kwargs):
"""Returns the mean loss on the given test data and labels.
# Arguments
x: array-like, shape `(n_samples, n_features)`
Test samples where `n_samples` is the number of samples
and `n_features` is the number of features.
y: array-like, shape `(n_samples,)`
True labels for `x`.
**kwargs: dictionary arguments
Legal arguments are the arguments of `Sequential.evaluate`.
# Returns
score: float
Mean accuracy of predictions on `x` wrt. `y`.
"""
kwargs = self.filter_sk_params(Sequential.evaluate, kwargs)
loss = self.model.evaluate(x, y, **kwargs)
if isinstance(loss, list):
return -loss[0]
return -loss
