Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

883 lines (708 sloc) 31.26 kb
"""
The :mod:`sklearn.pls` module implements Partial Least Squares (PLS).
"""
# Author: Edouard Duchesnay <edouard.duchesnay@cea.fr>
# License: BSD Style.
from .base import BaseEstimator, RegressorMixin, TransformerMixin
from .utils import check_arrays
import warnings
import numpy as np
from scipy import linalg
__all__ = ['CCA', 'PLSCanonical', 'PLSRegression', 'PLSSVD']
def _nipals_twoblocks_inner_loop(X, Y, mode="A", max_iter=500, tol=1e-06,
norm_y_weights=False):
"""Inner loop of the iterative NIPALS algorithm. Provides an alternative
to the svd(X'Y); returns the first left and rigth singular vectors of X'Y.
See PLS for the meaning of the parameters.
It is similar to the Power method for determining the eigenvectors and
eigenvalues of a X'Y
"""
y_score = Y[:, [0]]
x_weights_old = 0
ite = 1
X_pinv = Y_pinv = None
# Inner loop of the Wold algo.
while True:
# 1.1 Update u: the X weights
if mode == "B":
if X_pinv is None:
X_pinv = linalg.pinv(X) # compute once pinv(X)
x_weights = np.dot(X_pinv, y_score)
else: # mode A
# Mode A regress each X column on y_score
x_weights = np.dot(X.T, y_score) / np.dot(y_score.T, y_score)
# 1.2 Normalize u
x_weights /= np.sqrt(np.dot(x_weights.T, x_weights))
# 1.3 Update x_score: the X latent scores
x_score = np.dot(X, x_weights)
# 2.1 Update y_weights
if mode == "B":
if Y_pinv is None:
Y_pinv = linalg.pinv(Y) # compute once pinv(Y)
y_weights = np.dot(Y_pinv, x_score)
else:
# Mode A regress each Y column on x_score
y_weights = np.dot(Y.T, x_score) / np.dot(x_score.T, x_score)
## 2.2 Normalize y_weights
if norm_y_weights:
y_weights /= np.sqrt(np.dot(y_weights.T, y_weights))
# 2.3 Update y_score: the Y latent scores
y_score = np.dot(Y, y_weights) / np.dot(y_weights.T, y_weights)
## y_score = np.dot(Y, y_weights) / np.dot(y_score.T, y_score) ## BUG
x_weights_diff = x_weights - x_weights_old
if np.dot(x_weights_diff.T, x_weights_diff) < tol or Y.shape[1] == 1:
break
if ite == max_iter:
warnings.warn('Maximum number of iterations reached')
break
x_weights_old = x_weights
ite += 1
return x_weights, y_weights
def _svd_cross_product(X, Y):
C = np.dot(X.T, Y)
U, s, Vh = linalg.svd(C, full_matrices=False)
u = U[:, [0]]
v = Vh.T[:, [0]]
return u, v
def _center_scale_xy(X, Y, scale=True):
""" Center X, Y and scale if the scale parameter==True
Returns
-------
X, Y, x_mean, y_mean, x_std, y_std
"""
# center
x_mean = X.mean(axis=0)
X -= x_mean
y_mean = Y.mean(axis=0)
Y -= y_mean
# scale
if scale:
x_std = X.std(axis=0, ddof=1)
x_std[x_std == 0.0] = 1.0
X /= x_std
y_std = Y.std(axis=0, ddof=1)
y_std[y_std == 0.0] = 1.0
Y /= y_std
else:
x_std = np.ones(X.shape[1])
y_std = np.ones(Y.shape[1])
return X, Y, x_mean, y_mean, x_std, y_std
class _PLS(BaseEstimator, TransformerMixin, RegressorMixin):
"""Partial Least Squares (PLS)
This class implements the generic PLS algorithm, constructors' parameters
allow to obtain a specific implementation such as:
- PLS2 regression, i.e., PLS 2 blocks, mode A, with asymmetric deflation
and unnormlized y weights such as defined by [Tenenhaus 1998] p. 132.
With univariate response it implements PLS1.
- PLS canonical, i.e., PLS 2 blocks, mode A, with symetric deflation and
normlized y weights such as defined by [Tenenhaus 1998] (p. 132) and
[Wegelin et al. 2000]. This parametrization implements the original Wold
algorithm.
We use the terminology defined by [Wegelin et al. 2000].
This implementation uses the PLS Wold 2 blocks algorithm based on two
nested loops:
(i) The outer loop iterate over components.
(ii) The inner loop estimates the weights vectors. This can be done
with two algo. (a) the inner loop of the original NIPALS algo. or (b) a
SVD on residuals cross-covariance matrices.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q]
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
n_components : int, number of components to keep. (default 2).
scale : boolean, scale data? (default True)
deflation_mode : str, "canonical" or "regression". See notes.
mode : "A" classical PLS and "B" CCA. See notes.
norm_y_weights: boolean, normalize Y weights to one? (default False)
algorithm : string, "nipals" or "svd"
The algorithm used to estimate the weights. It will be called
n_components times, i.e. once for each iteration of the outer loop.
max_iter : an integer, the maximum number of iterations (default 500)
of the NIPALS inner loop (used only if algorithm="nipals")
tol : non-negative real, default 1e-06
The tolerance used in the iterative algorithm.
copy : boolean
Whether the deflation should be done on a copy. Let the default
value to True unless you don't care about side effects.
Attributes
----------
`x_weights_` : array, [p, n_components]
X block weights vectors.
`y_weights_` : array, [q, n_components]
Y block weights vectors.
`x_loadings_` : array, [p, n_components]
X block loadings vectors.
`y_loadings_` : array, [q, n_components]
Y block loadings vectors.
`x_scores_` : array, [n_samples, n_components]
X scores.
`y_scores_` : array, [n_samples, n_components]
Y scores.
`x_rotations_` : array, [p, n_components]
X block to latents rotations.
`y_rotations_` : array, [q, n_components]
Y block to latents rotations.
coefs: array, [p, q]
The coefficients of the linear model: Y = X coefs + Err
References
----------
Jacob A. Wegelin. A survey of Partial Least Squares (PLS) methods, with
emphasis on the two-block case. Technical Report 371, Department of
Statistics, University of Washington, Seattle, 2000.
In French but still a reference:
Tenenhaus, M. (1998). La regression PLS: theorie et pratique. Paris:
Editions Technic.
See also
--------
PLSCanonical
PLSRegression
CCA
PLS_SVD
"""
def __init__(self, n_components=2, scale=True, deflation_mode="regression",
mode="A", algorithm="nipals", norm_y_weights=False,
max_iter=500, tol=1e-06, copy=True):
self.n_components = n_components
self.deflation_mode = deflation_mode
self.mode = mode
self.norm_y_weights = norm_y_weights
self.scale = scale
self.algorithm = algorithm
self.max_iter = max_iter
self.tol = tol
self.copy = copy
def fit(self, X, Y):
# copy since this will contains the residuals (deflated) matrices
X, Y = check_arrays(X, Y, dtype=np.float, copy=self.copy,
sparse_format='dense')
if X.ndim != 2:
raise ValueError('X must be a 2D array')
if Y.ndim == 1:
Y = Y.reshape((Y.size, 1))
if Y.ndim != 2:
raise ValueError('Y must be a 1D or a 2D array')
n = X.shape[0]
p = X.shape[1]
q = Y.shape[1]
if n != Y.shape[0]:
raise ValueError(
'Incompatible shapes: X has %s samples, while Y '
'has %s' % (X.shape[0], Y.shape[0]))
if self.n_components < 1 or self.n_components > p:
raise ValueError('invalid number of components')
if self.algorithm not in ("svd", "nipals"):
raise ValueError("Got algorithm %s when only 'svd' "
"and 'nipals' are known" % self.algorithm)
if self.algorithm == "svd" and self.mode == "B":
raise ValueError('Incompatible configuration: mode B is not '
'implemented with svd algorithm')
if not self.deflation_mode in ["canonical", "regression"]:
raise ValueError('The deflation mode is unknown')
# Scale (in place)
X, Y, self.x_mean_, self.y_mean_, self.x_std_, self.y_std_\
= _center_scale_xy(X, Y, self.scale)
# Residuals (deflated) matrices
Xk = X
Yk = Y
# Results matrices
self.x_scores_ = np.zeros((n, self.n_components))
self.y_scores_ = np.zeros((n, self.n_components))
self.x_weights_ = np.zeros((p, self.n_components))
self.y_weights_ = np.zeros((q, self.n_components))
self.x_loadings_ = np.zeros((p, self.n_components))
self.y_loadings_ = np.zeros((q, self.n_components))
# NIPALS algo: outer loop, over components
for k in xrange(self.n_components):
#1) weights estimation (inner loop)
# -----------------------------------
if self.algorithm == "nipals":
x_weights, y_weights = _nipals_twoblocks_inner_loop(
X=Xk, Y=Yk, mode=self.mode,
max_iter=self.max_iter, tol=self.tol,
norm_y_weights=self.norm_y_weights)
elif self.algorithm == "svd":
x_weights, y_weights = _svd_cross_product(X=Xk, Y=Yk)
# compute scores
x_scores = np.dot(Xk, x_weights)
if self.norm_y_weights:
y_ss = 1
else:
y_ss = np.dot(y_weights.T, y_weights)
y_scores = np.dot(Yk, y_weights) / y_ss
# test for null variance
if np.dot(x_scores.T, x_scores) < np.finfo(np.double).eps:
warnings.warn('X scores are null at iteration %s' % k)
#2) Deflation (in place)
# ----------------------
# Possible memory footprint reduction may done here: in order to
# avoid the allocation of a data chunk for the rank-one
# approximations matrix which is then substracted to Xk, we suggest
# to perform a column-wise deflation.
#
# - regress Xk's on x_score
x_loadings = np.dot(Xk.T, x_scores) / np.dot(x_scores.T, x_scores)
# - substract rank-one approximations to obtain remainder matrix
Xk -= np.dot(x_scores, x_loadings.T)
if self.deflation_mode == "canonical":
# - regress Yk's on y_score, then substract rank-one approx.
y_loadings = np.dot(Yk.T, y_scores) \
/ np.dot(y_scores.T, y_scores)
Yk -= np.dot(y_scores, y_loadings.T)
if self.deflation_mode == "regression":
# - regress Yk's on x_score, then substract rank-one approx.
y_loadings = np.dot(Yk.T, x_scores) \
/ np.dot(x_scores.T, x_scores)
Yk -= np.dot(x_scores, y_loadings.T)
# 3) Store weights, scores and loadings # Notation:
self.x_scores_[:, k] = x_scores.ravel() # T
self.y_scores_[:, k] = y_scores.ravel() # U
self.x_weights_[:, k] = x_weights.ravel() # W
self.y_weights_[:, k] = y_weights.ravel() # C
self.x_loadings_[:, k] = x_loadings.ravel() # P
self.y_loadings_[:, k] = y_loadings.ravel() # Q
# Such that: X = TP' + Err and Y = UQ' + Err
# 4) rotations from input space to transformed space (scores)
# T = X W(P'W)^-1 = XW* (W* : p x k matrix)
# U = Y C(Q'C)^-1 = YC* (W* : q x k matrix)
self.x_rotations_ = np.dot(self.x_weights_,
linalg.inv(np.dot(self.x_loadings_.T, self.x_weights_)))
if Y.shape[1] > 1:
self.y_rotations_ = np.dot(self.y_weights_,
linalg.inv(np.dot(self.y_loadings_.T, self.y_weights_)))
else:
self.y_rotations_ = np.ones(1)
if True or self.deflation_mode == "regression":
# Estimate regression coefficient
# Regress Y on T
# Y = TQ' + Err,
# Then express in function of X
# Y = X W(P'W)^-1Q' + Err = XB + Err
# => B = W*Q' (p x q)
self.coefs = np.dot(self.x_rotations_, self.y_loadings_.T)
self.coefs = 1. / self.x_std_.reshape((p, 1)) * \
self.coefs * self.y_std_
return self
def transform(self, X, Y=None, copy=True):
"""Apply the dimension reduction learned on the train data.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q], optional
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
copy : boolean
Whether to copy X and Y, or perform in-place normalization.
Returns
-------
x_scores if Y is not given, (x_scores, y_scores) otherwise.
"""
# Normalize
if copy:
Xc = (np.asarray(X) - self.x_mean_) / self.x_std_
if Y is not None:
Yc = (np.asarray(Y) - self.y_mean_) / self.y_std_
else:
X = np.asarray(X)
Xc -= self.x_mean_
Xc /= self.x_std_
if Y is not None:
Y = np.asarray(Y)
Yc -= self.y_mean_
Yc /= self.y_std_
# Apply rotation
x_scores = np.dot(Xc, self.x_rotations_)
if Y is not None:
y_scores = np.dot(Yc, self.y_rotations_)
return x_scores, y_scores
return x_scores
def predict(self, X, copy=True):
"""Apply the dimension reduction learned on the train data.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
copy : boolean
Whether to copy X and Y, or perform in-place normalization.
Notes
-----
This call require the estimation of a p x q matrix, which may
be an issue in high dimensional space.
"""
# Normalize
if copy:
Xc = (np.asarray(X) - self.x_mean_)
else:
X = np.asarray(X)
Xc -= self.x_mean_
Xc /= self.x_std_
Ypred = np.dot(Xc, self.coefs)
return Ypred + self.y_mean_
def fit_transform(self, X, y=None, **fit_params):
"""Learn and apply the dimension reduction on the train data.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q], optional
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
copy : boolean
Whether to copy X and Y, or perform in-place normalization.
Returns
-------
x_scores if Y is not given, (x_scores, y_scores) otherwise.
"""
return self.fit(X, y, **fit_params).transform(X, y)
class PLSRegression(_PLS):
"""PLS regression
PLSRegression implements the PLS 2 blocks regression known as PLS2 or PLS1
in case of one dimensional response.
This class inherits from _PLS with mode="A", deflation_mode="regression",
norm_y_weights=False and algorithm="nipals".
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q]
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
n_components : int, (default 2)
Number of components to keep.
scale : boolean, (default True)
whether to scale the data
max_iter : an integer, (default 500)
the maximum number of iterations of the NIPALS inner loop (used
only if algorithm="nipals")
tol : non-negative real
Tolerance used in the iterative algorithm default 1e-06.
copy : boolean, default True
Whether the deflation should be done on a copy. Let the default
value to True unless you don't care about side effect
Attributes
----------
`x_weights_` : array, [p, n_components]
X block weights vectors.
`y_weights_` : array, [q, n_components]
Y block weights vectors.
`x_loadings_` : array, [p, n_components]
X block loadings vectors.
`y_loadings_` : array, [q, n_components]
Y block loadings vectors.
`x_scores_` : array, [n_samples, n_components]
X scores.
`y_scores_` : array, [n_samples, n_components]
Y scores.
`x_rotations_` : array, [p, n_components]
X block to latents rotations.
`y_rotations_` : array, [q, n_components]
Y block to latents rotations.
coefs: array, [p, q]
The coeficients of the linear model: Y = X coefs + Err
Notes
-----
For each component k, find weights u, v that optimizes:
``max corr(Xk u, Yk v) * var(Xk u) var(Yk u)``, such that ``|u| = 1``
Note that it maximizes both the correlations between the scores and the
intra-block variances.
The residual matrix of X (Xk+1) block is obtained by the deflation on
the current X score: x_score.
The residual matrix of Y (Yk+1) block is obtained by deflation on the
current X score. This performs the PLS regression known as PLS2. This
mode is prediction oriented.
This implementation provides the same results that 3 PLS packages
provided in the R language (R-project):
- "mixOmics" with function pls(X, Y, mode = "regression")
- "plspm " with function plsreg2(X, Y)
- "pls" with function oscorespls.fit(X, Y)
Examples
--------
>>> from sklearn.pls import PLSCanonical, PLSRegression, CCA
>>> X = [[0., 0., 1.], [1.,0.,0.], [2.,2.,2.], [2.,5.,4.]]
>>> Y = [[0.1, -0.2], [0.9, 1.1], [6.2, 5.9], [11.9, 12.3]]
>>> pls2 = PLSRegression(n_components=2)
>>> pls2.fit(X, Y)
... # doctest: +NORMALIZE_WHITESPACE
PLSRegression(copy=True, max_iter=500, n_components=2, scale=True,
tol=1e-06)
>>> Y_pred = pls2.predict(X)
References
----------
Jacob A. Wegelin. A survey of Partial Least Squares (PLS) methods, with
emphasis on the two-block case. Technical Report 371, Department of
Statistics, University of Washington, Seattle, 2000.
In french but still a reference:
Tenenhaus, M. (1998). La regression PLS: theorie et pratique. Paris:
Editions Technic.
"""
def __init__(self, n_components=2, scale=True,
max_iter=500, tol=1e-06, copy=True):
_PLS.__init__(self, n_components=n_components, scale=scale,
deflation_mode="regression", mode="A",
norm_y_weights=False,
max_iter=max_iter, tol=tol, copy=copy)
class PLSCanonical(_PLS):
""" PLSCanonical implements the 2 blocks canonical PLS of the original Wold
algorithm [Tenenhaus 1998] p.204, refered as PLS-C2A in [Wegelin 2000].
This class inherits from PLS with mode="A" and deflation_mode="canonical",
norm_y_weights=True and algorithm="nipals", but svd should provide similar
results up to numerical errors.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q]
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
n_components : int, number of components to keep. (default 2).
scale : boolean, scale data? (default True)
algorithm : string, "nipals" or "svd"
The algorithm used to estimate the weights. It will be called
n_components times, i.e. once for each iteration of the outer loop.
max_iter : an integer, (default 500)
the maximum number of iterations of the NIPALS inner loop (used
only if algorithm="nipals")
tol : non-negative real, default 1e-06
the tolerance used in the iterative algorithm
copy : boolean, default True
Whether the deflation should be done on a copy. Let the default
value to True unless you don't care about side effect
Attributes
----------
`x_weights_` : array, shape = [p, n_components]
X block weights vectors.
`y_weights_` : array, shape = [q, n_components]
Y block weights vectors.
`x_loadings_` : array, shape = [p, n_components]
X block loadings vectors.
`y_loadings_` : array, shape = [q, n_components]
Y block loadings vectors.
`x_scores_` : array, shape = [n_samples, n_components]
X scores.
`y_scores_` : array, shape = [n_samples, n_components]
Y scores.
`x_rotations_` : array, shape = [p, n_components]
X block to latents rotations.
`y_rotations_` : array, shape = [q, n_components]
Y block to latents rotations.
Notes
-----
For each component k, find weights u, v that optimize::
max corr(Xk u, Yk v) * var(Xk u) var(Yk u), such that ``|u| = |v| = 1``
Note that it maximizes both the correlations between the scores and the
intra-block variances.
The residual matrix of X (Xk+1) block is obtained by the deflation on the
current X score: x_score.
The residual matrix of Y (Yk+1) block is obtained by deflation on the
current Y score. This performs a canonical symetric version of the PLS
regression. But slightly different than the CCA. This is mode mostly used
for modeling.
This implementation provides the same results that the "plspm" package
provided in the R language (R-project), using the function plsca(X, Y).
Results are equal or colinear with the function
``pls(..., mode = "canonical")`` of the "mixOmics" package. The difference
relies in the fact that mixOmics implmentation does not exactly implement
the Wold algorithm since it does not normalize y_weights to one.
Examples
--------
>>> from sklearn.pls import PLSCanonical, PLSRegression, CCA
>>> X = [[0., 0., 1.], [1.,0.,0.], [2.,2.,2.], [2.,5.,4.]]
>>> Y = [[0.1, -0.2], [0.9, 1.1], [6.2, 5.9], [11.9, 12.3]]
>>> plsca = PLSCanonical(n_components=2)
>>> plsca.fit(X, Y)
... # doctest: +NORMALIZE_WHITESPACE
PLSCanonical(algorithm='nipals', copy=True, max_iter=500, n_components=2,
scale=True, tol=1e-06)
>>> X_c, Y_c = plsca.transform(X, Y)
References
----------
Jacob A. Wegelin. A survey of Partial Least Squares (PLS) methods, with
emphasis on the two-block case. Technical Report 371, Department of
Statistics, University of Washington, Seattle, 2000.
Tenenhaus, M. (1998). La regression PLS: theorie et pratique. Paris:
Editions Technic.
See also
--------
CCA
PLSSVD
"""
def __init__(self, n_components=2, scale=True, algorithm="nipals",
max_iter=500, tol=1e-06, copy=True):
_PLS.__init__(self, n_components=n_components, scale=scale,
deflation_mode="canonical", mode="A",
norm_y_weights=True, algorithm=algorithm,
max_iter=max_iter, tol=tol, copy=copy)
class CCA(_PLS):
"""CCA Canonical Correlation Analysis. CCA inherits from PLS with
mode="B" and deflation_mode="canonical".
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q]
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
n_components : int, (default 2).
number of components to keep.
scale : boolean, (default True)
whether to scale the data?
max_iter : an integer, (default 500)
the maximum number of iterations of the NIPALS inner loop (used
only if algorithm="nipals")
tol : non-negative real, default 1e-06.
the tolerance used in the iterative algorithm
copy : boolean
Whether the deflation be done on a copy. Let the default value
to True unless you don't care about side effects
Attributes
----------
`x_weights_` : array, [p, n_components]
X block weights vectors.
`y_weights_` : array, [q, n_components]
Y block weights vectors.
`x_loadings_` : array, [p, n_components]
X block loadings vectors.
`y_loadings_` : array, [q, n_components]
Y block loadings vectors.
`x_scores_` : array, [n_samples, n_components]
X scores.
`y_scores_` : array, [n_samples, n_components]
Y scores.
`x_rotations_` : array, [p, n_components]
X block to latents rotations.
`y_rotations_` : array, [q, n_components]
Y block to latents rotations.
Notes
-----
For each component k, find the weights u, v that maximizes
max corr(Xk u, Yk v), such that ``|u| = |v| = 1``
Note that it maximizes only the correlations between the scores.
The residual matrix of X (Xk+1) block is obtained by the deflation on the
current X score: x_score.
The residual matrix of Y (Yk+1) block is obtained by deflation on the
current Y score.
Examples
--------
>>> from sklearn.pls import PLSCanonical, PLSRegression, CCA
>>> X = [[0., 0., 1.], [1.,0.,0.], [2.,2.,2.], [3.,5.,4.]]
>>> Y = [[0.1, -0.2], [0.9, 1.1], [6.2, 5.9], [11.9, 12.3]]
>>> cca = CCA(n_components=1)
>>> cca.fit(X, Y)
... # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
CCA(copy=True, max_iter=500, n_components=1, scale=True, tol=1e-06)
>>> X_c, Y_c = cca.transform(X, Y)
References
----------
Jacob A. Wegelin. A survey of Partial Least Squares (PLS) methods, with
emphasis on the two-block case. Technical Report 371, Department of
Statistics, University of Washington, Seattle, 2000.
In french but still a reference:
Tenenhaus, M. (1998). La regression PLS: theorie et pratique. Paris:
Editions Technic.
See also
--------
PLSCanonical
PLSSVD
"""
def __init__(self, n_components=2, scale=True,
max_iter=500, tol=1e-06, copy=True):
_PLS.__init__(self, n_components=n_components, scale=scale,
deflation_mode="canonical", mode="B",
norm_y_weights=True, algorithm="nipals",
max_iter=max_iter, tol=tol, copy=copy)
class PLSSVD(BaseEstimator, TransformerMixin):
"""Partial Least Square SVD
Simply perform a svd on the crosscovariance matrix: X'Y
The are no iterative deflation here.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vector, where n_samples in the number of samples and
p is the number of predictors. X will be centered before any analysis.
Y : array-like of response, shape = [n_samples, q]
Training vector, where n_samples in the number of samples and
q is the number of response variables. X will be centered before any
analysis.
n_components : int, (default 2).
number of components to keep.
scale : boolean, (default True)
scale X and Y
Attributes
----------
`x_weights_` : array, [p, n_components]
X block weights vectors.
`y_weights_` : array, [q, n_components]
Y block weights vectors.
`x_scores_` : array, [n_samples, n_components]
X scores.
`y_scores_` : array, [n_samples, n_components]
Y scores.
See also
--------
PLSCanonical
CCA
"""
def __init__(self, n_components=2, scale=True, copy=True):
self.n_components = n_components
self.scale = scale
self.copy = copy
def fit(self, X, Y):
# copy since this will contains the centered data
X, Y = check_arrays(X, Y, dtype=np.float, copy=self.copy,
sparse_format='dense')
n = X.shape[0]
p = X.shape[1]
if X.ndim != 2:
raise ValueError('X must be a 2D array')
if n != Y.shape[0]:
raise ValueError(
'Incompatible shapes: X has %s samples, while Y '
'has %s' % (X.shape[0], Y.shape[0]))
if self.n_components < 1 or self.n_components > p:
raise ValueError('invalid number of components')
# Scale (in place)
X, Y, self.x_mean_, self.y_mean_, self.x_std_, self.y_std_ =\
_center_scale_xy(X, Y, self.scale)
# svd(X'Y)
C = np.dot(X.T, Y)
U, s, V = linalg.svd(C, full_matrices=False)
V = V.T
self.x_scores_ = np.dot(X, U)
self.y_scores_ = np.dot(Y, V)
self.x_weights_ = U
self.y_weights_ = V
return self
def transform(self, X, Y=None):
"""Apply the dimension reduction learned on the train data."""
Xr = (X - self.x_mean_) / self.x_std_
x_scores = np.dot(Xr, self.x_weights_)
if Y is not None:
Yr = (Y - self.y_mean_) / self.y_std_
y_scores = np.dot(Yr, self.y_weights_)
return x_scores, y_scores
return x_scores
def fit_transform(self, X, y=None, **fit_params):
"""Learn and apply the dimension reduction on the train data.
Parameters
----------
X : array-like of predictors, shape = [n_samples, p]
Training vectors, where n_samples in the number of samples and
p is the number of predictors.
Y : array-like of response, shape = [n_samples, q], optional
Training vectors, where n_samples in the number of samples and
q is the number of response variables.
Returns
-------
x_scores if Y is not given, (x_scores, y_scores) otherwise.
"""
return self.fit(X, y, **fit_params).transform(X, y)
Jump to Line
Something went wrong with that request. Please try again.