def dist2(x, y, x2sum=None):
"""
Calculate the square of the distances between the vectors in y and in
x. Vectors are stored along the rows.
x2sum is (optionally) x**2.sum(1)
returns D2
D2[i,j] = ((x[i] - y[j])**2).sum()
"""
if len(x) == x.size:
x = utils.columnVector(x)
if len(y) == y.size:
y = utils.columnVector(y)
if x2sum is None:
x2sum = (x**2).sum(1)[:, None]
else:
x2sum = utils.columnVector(x2sum)
y2sum = (y**2).sum(1)[:, None]
D2 = -2 * np.dot(x, y.T)
D2 = (D2.T + y2sum).T
D2 += x2sum
return D2
def multivariateNormalPDF(covar, mean, regScale=0.0):
"""
Generates a function f(x) which is a multivariate normal distribution.
x is assumed to store the vectors along the rows (ie x is a row vector or
a matrix composed of row vectors)
"""
mean = utils.columnVector(mean).T
# Regularize
if regScale != 0:
ind = np.arange(len(covar))
regularization = abs(covar[ind, ind]).mean() * regScale
covar[ind, ind] += regularization
# Calculate terms
covarInv = np.linalg.inv(covar)
det = np.linalg.det(2 * np.pi * covar)
norm = 1. / np.sqrt(det)
def PDF(x):
"""
x is assumed to store the vectors along the rows (ie x is a row vector or
a matrix composed of row vectors)
"""
if len(x) > 1:
return np.array([PDF(x1[None, :]) for x1 in x])
return float(norm \
* np.exp(-0.5 * np.dot((x-mean), np.dot(covarInv, (x-mean).T))))
return PDF
def pred(self, x):
"""
Predict the class of x
"""
probs = self.prob(x)
classInd = probs.argmax(1)
return utils.columnVector(self.classNames[classInd])
def initFit(self, centroids=None, dataWeights=None):
"""
Initialize a fit
"""
if centroids is None:
# Initialize centroid guesses
np.random.seed(self.seed)
ind = np.random.choice(len(self.x), self.nCluster)
self.centroids = self.x[ind]
else:
self.centroids = centroids
if dataWeights is None:
dataWeights = np.ones([len(self.x), 1])
else:
dataWeights = utils.columnVector(dataWeights)
self.dataWeights = dataWeights
self.error = []
self.oldcentroids = self.centroids.copy()
self.centroidMaxChange = []
self._assignCentroid()
def multi2binary(x):
"""
x should be ints 0, 1, 2, ... nClass-1
-1 in the input is treated as a missing value and is replaced with -1
Returns a numpy array shape (n x nClass) if nClass != 2
For nClass == 2, just return the data unaltered
"""
x = np.asarray(x)
nClass = x.max() + 1
if nClass == 2:
return utils.columnVector(x)
xbin = np.zeros([len(x), nClass])
for i in range(nClass):
mask = (x == i)
xbin[mask, i] = 1
mask = (x == -1)
xbin[mask, :] = -1
return xbin
def confidence(self, x):
"""
Confidence is given by the cluster confidence (what fraction of
elements in the cluster have the cluster name)
"""
clusterInd = self.predCluster(x)
conf = self.clusterConfidence[clusterInd]
return utils.columnVector(conf)
def pred(self, x):
"""
Predict the class x belongs to (only works if labelClusters has
been performed)
"""
clusterInd = self.predCluster(x)
ypred = self.clusterNames[clusterInd]
return utils.columnVector(ypred)
def pred(self, x):
"""
"""
# Condition the data, using the same conditioning as for the training
# set
x, dummy1, dummy2 = utils.condition(x, self._center, self._scale)
classInd = np.dot(x, self.w).argmax(1)
return utils.columnVector(self.classNames[classInd])
def linearBinaryPred(x, w):
"""
"""
ypred = np.dot(x, w)
mask = ypred > 0.5
ypred[mask] = 1
ypred[~mask] = 0
return utils.columnVector(ypred)
def confidence(self, x):
"""
Confidence is defined as (maximum probability)/(sum of probabilities)
for a given data point, which works under the assumption that every
data point belongs to one of the classes.
"""
P = self.prob(x)
psum = P.sum(1)
pnorm = P.max(1) / P.sum(1)
pnorm[psum == 0] = 0
return utils.columnVector(pnorm)
def softmaxProb(x, w):
"""
P[i, j] is the probability of belonging to class j given x[i], w[:, j]
"""
N, m = w.shape
k = m + 1
E = np.exp(np.dot(x, w))
A = 1. / (1 + E.sum(1))
A = utils.columnVector(A)
P = np.dot(A, np.ones([1, k]))
P[:, 0:-1] *= E
return P
def _xTc(x, y):
"""
A term used in updating the weights for the softmax gradient descents
Parameters
----------
x : array
Feature vectors. shape (n x d)
y : array
Binary labels. shape (n x nClass). y[i,j] = 1 for data[i] belonging
to class[j], else it equals 0.
"""
A = utils.columnVector(1 - y[:, -1])
B = y[:, 0:-1]
C = A * B
return np.dot(x.T, C)
def pred(self, x):
"""
Pred class of x
"""
if (self.arrayBatchSize is not None) and (len(x) > self.arrayBatchSize):
# Calculate y_predicted in batches
ypred = np.zeros(len(x))
for slicer in utils.arrayBatch(x, self.arrayBatchSize):
ypred[slicer] = self.pred(x[slicer]).flatten()
else:
h = self.featureMap(x)
ypred = self.sgd.classifier(h, self.results['w'])
return utils.columnVector(ypred)
def linBinSquaredLoss(x, y, w):
"""
"""
ypred = utils.columnVector(np.dot(x, w))
L = ((ypred - y)**2).mean()
return L
def fit(self, x, y, regScale=None, threshold=None, dataWeights=None):
"""
Perform a linear (ridge) regression
Parameters
----------
x : array
Training features, shape (n, d)
y : array
Labels. shape (n, 1)
regScale : float
Amount to scale regularization by
Saves
-------
w : weights
Approximate solution to equation y = x.dot.w
"""
# Initialize
y = utils.columnVector(y)
self._xraw = x
if regScale is not None:
self.regScale = regScale
x, center, scale = utils.condition(x)
self.x = x
self._center = center
self._scale = scale
self.y = y
# Apply weights to data points
if dataWeights is not None:
dataWeights = utils.columnVector(dataWeights)
sqrtWeights = np.sqrt(dataWeights)
x = x * sqrtWeights
y = y * sqrtWeights
self.dataWeights = dataWeights
self.regularization = self.regScale / (x**2).mean()
# Perform the regression
M = np.dot(x.T, x)
ind = np.arange(len(M))
M[ind, ind] += self.regularization
xTy = np.dot(x.T, y)
self.w = np.dot(np.linalg.inv(M), xTy)
if np.any(np.isnan(self.w)):
raise RuntimeError, "NaN encounter in w in fit"
# Get scalar offset
if self.scalarOffset:
self.w0 = (y - np.dot(x, self.w)).mean()
else:
self.w0 = 0.
if self.classify:
# Set up the classifier (using the un-weighted data)
self.classifier = LinearBinaryClassifier(self.y,
self.ypred(self.x))
