tick.robust.ModelModifiedHuber

class tick.robust.ModelModifiedHuber(fit_intercept: bool = True, n_threads: int = 1)[source]

Modified hinge loss model for binary classification. This loss is particularly for classification problems with outliers. This class gives first order information (gradient and loss) for this model and can be passed to any solver through the solver’s set_model method.

Given training data \((x_i, y_i) \in \mathbb R^d \times \{ -1, 1 \}\) for \(i=1, \ldots, n\), this model considers a goodness-of-fit

\[f(w, b) = \frac 1n \sum_{i=1}^n \ell(y_i, b + x_i^\top w),\]

where \(w \in \mathbb R^d\) is a vector containing the model-weights, \(b \in \mathbb R\) is the intercept (used only whenever fit_intercept=True) and \(\ell : \mathbb R^2 \rightarrow \mathbb R\) is the loss given by

\[\begin{split}\ell(y, y') = \begin{cases} - 4 y y' &\text{ if } y y' \leq -1 \\ (1 - y y')^2 &\text{ if } -1 < y y' < 1 \\ 0 &\text{ if } y y' \geq 1 \end{cases}\end{split}\]

for \(y \in \{ -1, 1\}\) and \(y' \in \mathbb R\). Data is passed to this model through the fit(X, y) method where X is the features matrix (dense or sparse) and y is the vector of labels.

Parameters

fit_intercept : bool

If True, the model uses an intercept

Attributes

features : {numpy.ndarray, scipy.sparse.csr_matrix}, shape=(n_samples, n_features)

The features matrix, either dense or sparse

labels : numpy.ndarray, shape=(n_samples,) (read-only)

The labels vector

n_samples : int (read-only)

Number of samples

n_features : int (read-only)

Number of features

n_coeffs : int (read-only)

Total number of coefficients of the model

n_threads : int, default=1 (read-only)

Number of threads used for parallel computation.

  • if int <= 0: the number of threads available on the CPU

  • otherwise the desired number of threads

__init__(fit_intercept: bool = True, n_threads: int = 1)[source]

Initialize self. See help(type(self)) for accurate signature.

fit(features, labels)[source]

Set the data into the model object

Parameters

features : {numpy.ndarray, scipy.sparse.csr_matrix}, shape=(n_samples, n_features)

The features matrix, either dense or sparse

labels : numpy.ndarray, shape=(n_samples,)

The labels vector

Returns

output : ModelModifiedHuber

The current instance with given data

get_lip_best() → float

Returns the best Lipschitz constant, using all samples Warning: this might take some time, since it requires a SVD computation.

Returns

output : float

The best Lipschitz constant

get_lip_max() → float

Returns the maximum Lipschitz constant of individual losses. This is particularly useful for step-size tuning of some solvers.

Returns

output : float

The maximum Lipschitz constant

get_lip_mean() → float

Returns the average Lipschitz constant of individual losses. This is particularly useful for step-size tuning of some solvers.

Returns

output : float

The average Lipschitz constant

grad(coeffs: numpy.ndarray, out: numpy.ndarray = None) → numpy.ndarray

Computes the gradient of the model at coeffs

Parameters

coeffs : numpy.ndarray

Vector where gradient is computed

out : numpy.ndarray or None

If None a new vector containing the gradient is returned, otherwise, the result is saved in out and returned

Returns

output : numpy.ndarray

The gradient of the model at coeffs

Notes

The fit method must be called to give data to the model, before using grad. An error is raised otherwise.

loss(coeffs: numpy.ndarray) → float

Computes the value of the goodness-of-fit at coeffs

Parameters

coeffs : numpy.ndarray

The loss is computed at this point

Returns

output : float

The value of the loss

Notes

The fit method must be called to give data to the model, before using loss. An error is raised otherwise.

loss_and_grad(coeffs: numpy.ndarray, out: numpy.ndarray = None) → tuple

Computes the value and the gradient of the function at coeffs

Parameters

coeffs : numpy.ndarray

Vector where the loss and gradient are computed

out : numpy.ndarray or None

If None a new vector containing the gradient is returned, otherwise, the result is saved in out and returned

Returns

loss : float

The value of the loss

grad : numpy.ndarray

The gradient of the model at coeffs

Notes

The fit method must be called to give data to the model, before using loss_and_grad. An error is raised otherwise.

Examples using tick.robust.ModelModifiedHuber