atoms.sparse_group_lasso¶
Module: atoms.sparse_group_lasso¶
Inheritance diagram for regreg.atoms.sparse_group_lasso:
Implementation of the sparse group LASSO atom.
This penalty is defined by groups and individual feature weights and is $$ eta mapsto sum_j lambda_j |eta_j| + sum_g lpha_g |eta_g|_2 $$
Classes¶
sparse_group_lasso¶
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class
regreg.atoms.sparse_group_lasso.sparse_group_lasso(groups, lasso_weights, weights={}, lagrange=None, bound=None, offset=None, quadratic=None, initial=None)¶ Bases:
regreg.atoms.group_lasso.group_lasso,regreg.atoms.seminorms.seminormSparse group LASSO
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__init__(groups, lasso_weights, weights={}, lagrange=None, bound=None, offset=None, quadratic=None, initial=None)¶ Initialize self. See help(type(self)) for accurate signature.
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classmethod
affine(linear_operator, offset, lagrange=None, diag=False, bound=None, quadratic=None)¶ This is the same as the linear class method but with offset as a positional argument
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apply_offset(x)¶ If self.offset is not None, return x-self.offset, else return x.
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property
bound¶
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bound_prox(x, bound=None)¶ Return unique minimizer
\[{\beta}^{\delta}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{1}{2} \|\theta-\beta\|^2_2 \ \text{s.t.} \ \left[ \sum_j \alpha_j |\beta_j| + \sum_g \lambda_g \|\beta[g]\|_2 \right] \leq \delta\]where \(\delta\) is the bound parameter and \(\theta\) is arg.
If the argument bound is None and the atom is in bound mode,
self.boundis used as the bound parameter, else an exception is raised.The class atom’s bound_prox just returns the appropriate bound parameter for use by the subclasses.
- Parameters
arg : np.ndarray(np.float)
Argument of the proximal map.
bound : float (optional)
Bound for the constraint on the seminorm. Defaults to self.bound.
- Returns
Z : np.ndarray(np.float)
The proximal map of arg.
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static
check_subgradient(atom, prox_center)¶ For a given seminorm, verify the KKT condition for the problem for the proximal problem
\[\text{minimize}_u \frac{1}{2} \|u-z\|^2_2 + h(z)\]where \(z\) is the prox_center and \(h\) is atom which may be in Lagrange or bound form.
If the atom is in Lagrange form, this function should return two values equal to the seminorm of the minimizer. If it is bound form it should return two values equal to the dual seminorm of the residual, i.e. the prox_center minus the minimizer.
- Parameters
atom : seminorm
prox_center : np.ndarray(np.float)
Center for the proximal map.
- Returns
v1, v2 : float
Two values that should be equal if the proximal map is correct.
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property
conjugate¶
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constraint(x, bound=None)¶ Verify :math:` left[ sum_j alpha_j |\beta_j| + sum_g lambda_g |beta[g]|_2 right] leq delta`, where \(\delta\) is bound.
If the result is True, returns 0, else returns np.inf.
The class seminorm’s constraint just returns the appropriate bound parameter for use by the subclasses.
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property
dual¶
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get_bound()¶ Get method of the bound property.
>>> import regreg.api as rr >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=2.3) >>> constraint.bound 2.3
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get_conjugate()¶ Return the conjugate of an given atom.
>>> import regreg.api as rr >>> penalty = rr.sparse_group_lasso([1, 1, 2, 2, 2], [0, 0.5, 0.2, 0.2, 0.2], lagrange=3.4) >>> penalty.get_conjugate() sparse_group_lasso_dual(..., bound=3.4...)
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get_dual()¶ Return the dual of an atom. This dual is formed by making introducing new variables \(v=Ax\) where \(A\) is self.linear_transform.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=2.3) >>> penalty group_lasso(..., lagrange=2.3...) >>> penalty.dual (<regreg.affine.identity object at 0x...>, group_lasso_dual(..., bound=2.3...))
If there is a linear part to the penalty, the linear_transform may not be identity. For example, the 1D fused LASSO penalty:
>>> D = (np.identity(4) + np.diag(-np.ones(3),1))[:-1] >>> D array([[ 1., -1., 0., 0.], [ 0., 1., -1., 0.], [ 0., 0., 1., -1.]]) >>> linear_atom = rr.l1norm.linear(D, lagrange=2.3) >>> linear_atom affine_atom(l1norm((3,), lagrange=2.3...), array([[ 1., -1., 0., 0.], [ 0., 1., -1., 0.], [ 0., 0., 1., -1.]])) >>> linear_atom.dual (<regreg.affine.linear_transform object at 0x...>, supnorm((3,), bound=2.3...))
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get_lagrange()¶ Get method of the lagrange property.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=3.4) >>> penalty.lagrange 3.4
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get_offset()¶
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get_quadratic()¶ Get the quadratic part of the composite.
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property
lagrange¶
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lagrange_prox(x, lipschitz=1, lagrange=None)¶ Return unique minimizer
\[{\beta}^{\lambda}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \lambda \left[ \sum_j \alpha_j |\beta_j| + \sum_g \lambda_g \|\beta[g]\|_2 \right] \]Above, \(\lambda\) is the Lagrange parameter and \(L\) is the Lipschitz parameter and \(\theta\) is arg.
If the argument lagrange is None and the atom is in lagrange mode,
self.lagrangeis used as the lagrange parameter, else an exception is raised.The class atom’s lagrange_prox just returns the appropriate lagrange parameter for use by the subclasses.
- Parameters
arg : np.ndarray(np.float)
Argument of the proximal map.
lipschitz : float
Coefficient in front of the quadratic.
lagrange : float (optional)
Lagrange factor in front of the seminorm. Defaults to self.lagrange.
- Returns
Z : np.ndarray(np.float)
The proximal map of arg.
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latexify(var=None, idx='')¶ Return a LaTeX representation of an object.
>>> import regreg.api as rr >>> penalty = rr.l1norm(10, lagrange=0.9) >>> penalty.latexify(var=r'\gamma') '\\lambda_{} \\|\\gamma\\|_1'
- Parameters
var : string
Argument of the functions
idx : string
Optional subscript index.
- Returns
L : string
A LaTeX representation of the atom.
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classmethod
linear(linear_operator, lagrange=None, diag=False, bound=None, quadratic=None, offset=None)¶
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property
linear_transform¶ The linear transform applied before a penalty is computed. Defaults to regreg.affine.identity
>>> from regreg.api import l1norm >>> penalty = l1norm(30, lagrange=3.4) >>> type(penalty.linear_transform) <class 'regreg.affine.identity'>
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nonsmooth_objective(arg, check_feasibility=False)¶ The nonsmooth objective function of the atom. Includes self.quadratic.objective(arg).
>>> import regreg.api as rr >>> penalty = rr.l1norm(4, lagrange=2) >>> penalty.nonsmooth_objective([3, 4, 5, 9]) 42.0 >>> 2 * sum([3, 4, 5, 9]) 42
- Parameters
arg : np.ndarray(np.float)
Argument of the seminorm.
check_feasibility : bool
If True, then return np.inf if appropriate.
- Returns
value : np.float
The seminorm of arg.
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objective(x, check_feasibility=False)¶
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objective_template= ' \\left[ \\sum_j \\alpha_j |%(var)s_j| + \\sum_g \\lambda_g \\|%(var)s[g]\\|_2 \\right]'¶
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objective_vars= {'dualnormklass': 'sparse_group_lasso_dual', 'initargs': '[1, 1, 2, 2, 2], [0, 0.5, 0.2, 0.2, 0.2]', 'linear': 'D', 'normklass': 'sparse_group_lasso', 'offset': '\\alpha', 'shape': 'p', 'var': '\\beta'}¶
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property
offset¶
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proximal(quadratic, prox_control=None)¶ The proximal operator. If the atom is in Lagrange mode, this has the form
\[\beta^{\lambda}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \lambda h(\beta-\alpha) + \langle \beta, \eta \rangle\]where \(\alpha\) is self.offset, \(\eta\) is quadratic.linear_term, \(\theta\) is quadratic.center and
\[h(\beta) = \sum_g w_g \|\beta[g]\|_2\]If the atom is in bound mode, then this has the form
\[\beta^{\delta}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \langle \beta, \eta \rangle \ \text{s.t.} \ h(\beta - \alpha) \leq \delta\]>>> import regreg.api as rr >>> penalty = rr.l1norm(4, lagrange=2) >>> Q = rr.identity_quadratic(1.5, [3, -4, -1, 1], 0, 0) >>> penalty.proximal(Q) array([ 1.6666..., -2.6666..., -0. , 0. ])
- Parameters
quadratic : regreg.identity_quadratic.identity_quadratic
A quadratic added to the atom before minimizing.
prox_control : [None, dict]
This argument is ignored for seminorms, but otherwise is passed to regreg.algorithms.FISTA if the atom needs to be solved iteratively.
- Returns
Z : np.ndarray(np.float)
The proximal map of the implied center of quadratic.
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proximal_optimum(quadratic)¶
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proximal_step(quadratic, prox_control=None)¶ Compute the proximal optimization
- Parameters
prox_control: [None, dict]
If not None, then a dictionary of parameters for the prox procedure
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property
quadratic¶ Quadratic part of the object, instance of regreg.identity_quadratic.identity_quadratic.
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seminorm(x, lagrange=None, check_feasibility=False)¶ Return \(\lambda \cdot \left[ \sum_j \alpha_j |\beta_j| + \sum_g \lambda_g \|\beta[g]\|_2 \right]\), where \(\lambda\) is lagrange. If check_feasibility is True, and seminorm is unbounded, will return np.inf if appropriate.
The class seminorm’s seminorm just returns the appropriate lagrange parameter for use by the subclasses.
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set_bound(bound)¶ Set method of the bound property.
>>> import regreg.api as rr >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=3.4) >>> constraint.bound 3.4 >>> constraint.bound = 2.3 >>> constraint.bound 2.3 >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=2.3) >>> penalty.bound = 3.4 Traceback (most recent call last): ... AttributeError: atom is in lagrange mode
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set_lagrange(lagrange)¶ Set method of the lagrange property.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=3.4) >>> penalty.lagrange 3.4 >>> penalty.lagrange = 2.3 >>> penalty.lagrange 2.3 >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=3.4) >>> constraint.lagrange = 3.4 Traceback (most recent call last): ... AttributeError: atom is in bound mode
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set_offset(value)¶
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set_quadratic(quadratic)¶ Set the quadratic part of the composite.
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set_weight(group, weight)¶ Set a group’s weight after initialization.
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classmethod
shift(offset, lagrange=None, diag=False, bound=None, quadratic=None)¶
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smooth_objective(x, mode='both', check_feasibility=False)¶ The zero function.
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smoothed(smoothing_quadratic)¶ Add quadratic smoothing term
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solve(quadratic=None, return_optimum=False, **fit_args)¶
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terms(arg)¶ Return the args that are summed in computing the seminorm.
>>> import regreg.api as rr >>> groups = [1,1,2,2,2] >>> penalty = rr.group_lasso(groups, lagrange=1.) >>> arg = [2,4,5,3,4] >>> penalty.terms(arg) [6.3245..., 12.2474...] >>> penalty.seminorm(arg) 18.5720... >>> np.sqrt((2**2 + 4**2)*2), np.sqrt((5**2 + 3**2 + 4**2) * 3.) (6.3245..., 12.2474...) >>> np.sqrt((2**2 + 4**2)*2) + np.sqrt((5**2 + 3**2 + 4**2) * 3.) 18.5720...
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tol= 1e-05¶
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sparse_group_lasso_dual¶
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class
regreg.atoms.sparse_group_lasso.sparse_group_lasso_dual(groups, lasso_weights, weights={}, lagrange=None, bound=None, offset=None, quadratic=None, initial=None)¶ Bases:
regreg.atoms.sparse_group_lasso.sparse_group_lassoThe dual of the slope penalty:math:ell_{infty} norm
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__init__(groups, lasso_weights, weights={}, lagrange=None, bound=None, offset=None, quadratic=None, initial=None)¶ Initialize self. See help(type(self)) for accurate signature.
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classmethod
affine(linear_operator, offset, lagrange=None, diag=False, bound=None, quadratic=None)¶ This is the same as the linear class method but with offset as a positional argument
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apply_offset(x)¶ If self.offset is not None, return x-self.offset, else return x.
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property
base_conjugate¶ For a sparse group LASSO dual in bound form, an atom that agrees with its primal Lagrange form.
Note: this conjugate does not take into account the atom’s quadratic and offset terms.
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property
bound¶
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bound_prox(x, bound=None)¶ Return unique minimizer
\[{\beta}^{\delta}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{1}{2} \|\theta-\beta\|^2_2 \ \text{s.t.} \ {\cal D}^{group sparse}(\beta) \leq \delta\]where \(\delta\) is the bound parameter and \(\theta\) is arg.
If the argument bound is None and the atom is in bound mode,
self.boundis used as the bound parameter, else an exception is raised.The class atom’s bound_prox just returns the appropriate bound parameter for use by the subclasses.
- Parameters
arg : np.ndarray(np.float)
Argument of the proximal map.
bound : float (optional)
Bound for the constraint on the seminorm. Defaults to self.bound.
- Returns
Z : np.ndarray(np.float)
The proximal map of arg.
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static
check_subgradient(atom, prox_center)¶ For a given seminorm, verify the KKT condition for the problem for the proximal problem
\[\text{minimize}_u \frac{1}{2} \|u-z\|^2_2 + h(z)\]where \(z\) is the prox_center and \(h\) is atom which may be in Lagrange or bound form.
If the atom is in Lagrange form, this function should return two values equal to the seminorm of the minimizer. If it is bound form it should return two values equal to the dual seminorm of the residual, i.e. the prox_center minus the minimizer.
- Parameters
atom : seminorm
prox_center : np.ndarray(np.float)
Center for the proximal map.
- Returns
v1, v2 : float
Two values that should be equal if the proximal map is correct.
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property
conjugate¶
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constraint(x, bound=None)¶ Verify \({\cal D}^{group sparse}(\beta) \leq \delta\), where \(\delta\) is bound.
If the result is True, returns 0, else returns np.inf.
The class seminorm’s constraint just returns the appropriate bound parameter for use by the subclasses.
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property
dual¶
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get_bound()¶ Get method of the bound property.
>>> import regreg.api as rr >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=2.3) >>> constraint.bound 2.3
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get_conjugate()¶ Return the conjugate of an given atom.
>>> import regreg.api as rr >>> penalty = rr.sparse_group_lasso([1, 1, 2, 2, 2], [0, 0.5, 0.2, 0.2, 0.2], lagrange=3.4) >>> penalty.get_conjugate() sparse_group_lasso_dual(..., bound=3.4...)
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get_dual()¶ Return the dual of an atom. This dual is formed by making introducing new variables \(v=Ax\) where \(A\) is self.linear_transform.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=2.3) >>> penalty group_lasso(..., lagrange=2.3...) >>> penalty.dual (<regreg.affine.identity object at 0x...>, group_lasso_dual(..., bound=2.3...))
If there is a linear part to the penalty, the linear_transform may not be identity. For example, the 1D fused LASSO penalty:
>>> D = (np.identity(4) + np.diag(-np.ones(3),1))[:-1] >>> D array([[ 1., -1., 0., 0.], [ 0., 1., -1., 0.], [ 0., 0., 1., -1.]]) >>> linear_atom = rr.l1norm.linear(D, lagrange=2.3) >>> linear_atom affine_atom(l1norm((3,), lagrange=2.3...), array([[ 1., -1., 0., 0.], [ 0., 1., -1., 0.], [ 0., 0., 1., -1.]])) >>> linear_atom.dual (<regreg.affine.linear_transform object at 0x...>, supnorm((3,), bound=2.3...))
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get_lagrange()¶ Get method of the lagrange property.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=3.4) >>> penalty.lagrange 3.4
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get_offset()¶
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get_quadratic()¶ Get the quadratic part of the composite.
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property
lagrange¶
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lagrange_prox(x, lipschitz=1, lagrange=None)¶ Return unique minimizer
\[{\beta}^{\lambda}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \lambda {\cal D}^{group sparse}(\beta) \]Above, \(\lambda\) is the Lagrange parameter and \(L\) is the Lipschitz parameter and \(\theta\) is arg.
If the argument lagrange is None and the atom is in lagrange mode,
self.lagrangeis used as the lagrange parameter, else an exception is raised.The class atom’s lagrange_prox just returns the appropriate lagrange parameter for use by the subclasses.
- Parameters
arg : np.ndarray(np.float)
Argument of the proximal map.
lipschitz : float
Coefficient in front of the quadratic.
lagrange : float (optional)
Lagrange factor in front of the seminorm. Defaults to self.lagrange.
- Returns
Z : np.ndarray(np.float)
The proximal map of arg.
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latexify(var=None, idx='')¶ Return a LaTeX representation of an object.
>>> import regreg.api as rr >>> penalty = rr.l1norm(10, lagrange=0.9) >>> penalty.latexify(var=r'\gamma') '\\lambda_{} \\|\\gamma\\|_1'
- Parameters
var : string
Argument of the functions
idx : string
Optional subscript index.
- Returns
L : string
A LaTeX representation of the atom.
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classmethod
linear(linear_operator, lagrange=None, diag=False, bound=None, quadratic=None, offset=None)¶
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property
linear_transform¶ The linear transform applied before a penalty is computed. Defaults to regreg.affine.identity
>>> from regreg.api import l1norm >>> penalty = l1norm(30, lagrange=3.4) >>> type(penalty.linear_transform) <class 'regreg.affine.identity'>
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nonsmooth_objective(arg, check_feasibility=False)¶ The nonsmooth objective function of the atom. Includes self.quadratic.objective(arg).
>>> import regreg.api as rr >>> penalty = rr.l1norm(4, lagrange=2) >>> penalty.nonsmooth_objective([3, 4, 5, 9]) 42.0 >>> 2 * sum([3, 4, 5, 9]) 42
- Parameters
arg : np.ndarray(np.float)
Argument of the seminorm.
check_feasibility : bool
If True, then return np.inf if appropriate.
- Returns
value : np.float
The seminorm of arg.
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objective(x, check_feasibility=False)¶
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objective_template= '{\\cal D}^{group sparse}(%(var)s)'¶
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objective_vars= {'dualnormklass': 'supnorm', 'initargs': '(30,)', 'linear': 'D', 'normklass': 'l1norm', 'offset': '\\alpha', 'shape': 'p', 'var': '\\beta'}¶
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property
offset¶
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proximal(quadratic, prox_control=None)¶ The proximal operator. If the atom is in Lagrange mode, this has the form
\[\beta^{\lambda}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \lambda h(\beta-\alpha) + \langle \beta, \eta \rangle\]where \(\alpha\) is self.offset, \(\eta\) is quadratic.linear_term, \(\theta\) is quadratic.center and
\[h(\beta) = \sum_g w_g \|\beta[g]\|_2\]If the atom is in bound mode, then this has the form
\[\beta^{\delta}(\theta) = \text{argmin}_{\beta \in \mathbb{R}^{p}} \frac{L}{2} \|\theta-\beta\|^2_2 + \langle \beta, \eta \rangle \ \text{s.t.} \ h(\beta - \alpha) \leq \delta\]>>> import regreg.api as rr >>> penalty = rr.l1norm(4, lagrange=2) >>> Q = rr.identity_quadratic(1.5, [3, -4, -1, 1], 0, 0) >>> penalty.proximal(Q) array([ 1.6666..., -2.6666..., -0. , 0. ])
- Parameters
quadratic : regreg.identity_quadratic.identity_quadratic
A quadratic added to the atom before minimizing.
prox_control : [None, dict]
This argument is ignored for seminorms, but otherwise is passed to regreg.algorithms.FISTA if the atom needs to be solved iteratively.
- Returns
Z : np.ndarray(np.float)
The proximal map of the implied center of quadratic.
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proximal_optimum(quadratic)¶
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proximal_step(quadratic, prox_control=None)¶ Compute the proximal optimization
- Parameters
prox_control: [None, dict]
If not None, then a dictionary of parameters for the prox procedure
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property
quadratic¶ Quadratic part of the object, instance of regreg.identity_quadratic.identity_quadratic.
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seminorm(x, lagrange=None, check_feasibility=False)¶ Return \(\lambda \cdot {\cal D}^{group sparse}(\beta)\), where \(\lambda\) is lagrange. If check_feasibility is True, and seminorm is unbounded, will return np.inf if appropriate.
The class seminorm’s seminorm just returns the appropriate lagrange parameter for use by the subclasses.
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set_bound(bound)¶ Set method of the bound property.
>>> import regreg.api as rr >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=3.4) >>> constraint.bound 3.4 >>> constraint.bound = 2.3 >>> constraint.bound 2.3 >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=2.3) >>> penalty.bound = 3.4 Traceback (most recent call last): ... AttributeError: atom is in lagrange mode
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set_lagrange(lagrange)¶ Set method of the lagrange property.
>>> import regreg.api as rr >>> penalty = rr.group_lasso([1, 1, 2, 2, 2], lagrange=3.4) >>> penalty.lagrange 3.4 >>> penalty.lagrange = 2.3 >>> penalty.lagrange 2.3 >>> constraint = rr.group_lasso([1, 1, 2, 2, 2], bound=3.4) >>> constraint.lagrange = 3.4 Traceback (most recent call last): ... AttributeError: atom is in bound mode
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set_offset(value)¶
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set_quadratic(quadratic)¶ Set the quadratic part of the composite.
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set_weight(group, weight)¶ Set a group’s weight after initialization.
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classmethod
shift(offset, lagrange=None, diag=False, bound=None, quadratic=None)¶
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smooth_objective(x, mode='both', check_feasibility=False)¶ The zero function.
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smoothed(smoothing_quadratic)¶ Add quadratic smoothing term
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solve(quadratic=None, return_optimum=False, **fit_args)¶
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terms(arg)¶ Return the args that are summed in computing the seminorm.
>>> import regreg.api as rr >>> groups = [1,1,2,2,2] >>> penalty = rr.group_lasso(groups, lagrange=1.) >>> arg = [2,4,5,3,4] >>> penalty.terms(arg) [6.3245..., 12.2474...] >>> penalty.seminorm(arg) 18.5720... >>> np.sqrt((2**2 + 4**2)*2), np.sqrt((5**2 + 3**2 + 4**2) * 3.) (6.3245..., 12.2474...) >>> np.sqrt((2**2 + 4**2)*2) + np.sqrt((5**2 + 3**2 + 4**2) * 3.) 18.5720...
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tol= 1e-05¶
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Function¶
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regreg.atoms.sparse_group_lasso.inside_set(atom, point)¶ Is the point in the dual ball?
If the atom is the primal (necessarily in lagrange form), we check whether point is in the dual ball (i.e. the one determining the norm.
If the atom is a dual (necessarily in bound form), we just check if we project onto the same point.