add DFMrff as a named method, promote quadprog to a standard dependency

- DFMrff exposes qunfold.KMM(kernel='rff') as a public, importable
  quapy.method.non_aggregative class, following Dussap et al. (2023);
  the import of qunfold stays lazy (inside __init__/fit) so the module
  remains usable without it, matching the EDx/EDy pattern. Registered
  in NON_AGGREGATIVE_METHODS and as optional in test_methods.py.
- quadprog (required by EDx/EDy) is no longer gated behind a lazy
  _get_quadprog() helper; it's now a direct install_requires entry,
  which also bumps the minimum supported Python to 3.9.
- Added a manual section for DFMrff, cross-referencing the Composable
  Methods section for the other (non-default) KMM kernels.

CHANGE_LOG.txt

@@ -1,3 +1,11 @@
+Change Log 0.2.4
+-----------------
+
+- Making DFM-RFF method explicit, and improved documentation.
+
+- Promoted quadprog (required by EDx/EDy) from an optional to a standard dependency; the minimum
+  supported Python version is now 3.9.
+
 Change Log 0.2.3
 -----------------
 

README.md

@@ -1,6 +1,6 @@
 # QuaPy
 
-## version 0.2.3
+## version 0.2.4
 
 QuaPy is an open source framework for quantification (a.k.a. supervised prevalence estimation, or learning to quantify)
 written in Python.
@@ -15,7 +15,7 @@ for facilitating the analysis and interpretation of the experimental results.
 
 ### Last updates:
 
-* Version 0.2.3 is released! major changes can be consulted [here](CHANGE_LOG.txt).
+* Version 0.2.4 is released! major changes can be consulted [here](CHANGE_LOG.txt).
 * The developer API documentation is available [here](https://hlt-isti.github.io/QuaPy/index.html)
 
 ### Installation

docs/source/manuals/methods.md

@@ -476,8 +476,7 @@ problem by quadratic programming. The method is proposed in
 In QuaPy, `EDy` works for binary and
 multiclass problems and lets the user choose the pairwise distance through the
 `distance` parameter (`'manhattan'`, `'euclidean'`, or a custom callable).
-Because the optimization relies on `quadprog`, this method requires the
-optional dependency `pip install quadprog`.
+The optimization relies on `quadprog`, a standard QuaPy dependency.
 
 #### SMM
 
@@ -670,7 +669,46 @@ a classifier. In this sense, `EDx` is to `EDy` what `DMx` is to `DMy`.
 
 `EDx` works for binary and multiclass problems, accepts the same `distance`
 options as `EDy` (`'manhattan'`, `'euclidean'`, or a custom callable), and
-requires the optional dependency `pip install quadprog`.
+relies on `quadprog`, a standard QuaPy dependency.
+
+### Distribution Feature Matching (DFMrff)
+
+QuaPy exposes `qp.method.non_aggregative.DFMrff`, a covariate-space
+distribution-matching quantifier proposed in:
+
+[_Dussap, B., Blanchard, G., & Chérief-Abdellatif, B. E. (2023). Label shift
+quantification with robustness guarantees via distribution feature matching.
+In Joint European Conference on Machine Learning and Knowledge Discovery in
+Databases (pp. 69-85). Springer._](https://doi.org/10.1007/978-3-031-43412-9_5)
+
+The method matches the training and test distributions through a kernel
+embedding, approximated via random Fourier features (hence "RFF") for
+computational efficiency; the authors report this to be the best-performing
+variant among the kernels they study (energy, Gaussian, Laplacian, and RFF),
+which is why `DFMrff` is the only one of them exposed as a named, public
+method. `DFMrff` accepts the following hyperparameters: `sigma` (the kernel
+smoothing parameter), `n_rff` (the number of random Fourier features,
+default 1000), `solver` and `solver_options` (passed to
+`scipy.optimize.minimize`), and `seed`.
+
+```python
+import quapy as qp
+from quapy.method.non_aggregative import DFMrff
+
+dataset = qp.datasets.fetch_UCIMulticlassDataset('dry-bean')
+train, test = dataset.train_test
+
+model = DFMrff(n_rff=1000, seed=0)
+model.fit(*train.Xy)
+estim_prevalence = model.predict(test.X)
+```
+
+Internally, `DFMrff` is a thin wrapper around `qunfold.KMM(kernel='rff')`
+(see the Composable Methods section below), and therefore requires the
+optional `qunfold` dependency. The other kernel choices for `KMM`, as well as
+arbitrary re-combinations of losses and feature representations, remain
+directly accessible through `quapy.method.composable.ComposableQuantifier`
+and `quapy.method.composable.QUnfoldWrapper`.
 
 ### ReadMe
 

quapy/__init__.py

@@ -17,7 +17,7 @@ try:
 except ImportError:
     plot = None
 
-__version__ = '0.2.3'
+__version__ = '0.2.4'
 
 
 def _default_cls():

quapy/method/__init__.py

@@ -75,7 +75,8 @@ MULTICLASS_METHODS = {
 NON_AGGREGATIVE_METHODS = {
     non_aggregative.MaximumLikelihoodPrevalenceEstimation,
     non_aggregative.DMx,
-    non_aggregative.EDx
+    non_aggregative.EDx,
+    non_aggregative.DFMrff,
 }
 
 META_METHODS = {

quapy/method/_energy.py

@@ -1,11 +1,11 @@
 from typing import Callable, Union
 
 import numpy as np
+import quadprog
 from sklearn.metrics.pairwise import euclidean_distances, manhattan_distances
 
 import quapy as qp
 import quapy.functional as F
-from quapy.method._helper import _get_quadprog
 
 
 class _EnergyDistanceCore:
@@ -114,7 +114,6 @@ class _EnergyDistanceCore:
 
     def _solve_ed(self, G, a, C, b):
         """Solve the energy-distance quadratic program."""
-        quadprog = _get_quadprog()
         sol = quadprog.solve_qp(G=G, a=a, C=C, b=b)
         prevalences = sol[0]
         prevalences = np.append(prevalences, 1 - prevalences.sum())

quapy/method/_helper.py

@@ -32,16 +32,6 @@ def _get_cvxpy():
     return cp
 
 
-def _get_quadprog():
-    try:
-        import quadprog
-    except ImportError as exc:
-        raise ImportError(
-            "EDy requires the optional 'quadprog' package."
-        ) from exc
-    return quadprog
-
-
 def _labels_to_indices(labels, classes):
     encoder = LabelEncoder().fit(classes)
     return encoder.transform(labels)

quapy/method/aggregative.py

@@ -2114,8 +2114,9 @@ class EDy(_EnergyDistanceCore, AggregativeSoftQuantifier):
     operates directly on posterior vectors rather than on histogram summaries.
 
     This implementation works for binary and multiclass single-label
-    quantification and relies on the optional ``quadprog`` dependency. It was
-    adapted to QuaPy's current aggregative API from the original implementation
+    quantification and relies on the ``quadprog`` package for solving the
+    underlying quadratic program. It was adapted to QuaPy's current aggregative
+    API from the original implementation
     available in `quantificationlib <https://github.com/AICGijon/quantificationlib>`_,
     and now shares its numerical core with the classifier-free
     :class:`quapy.method.non_aggregative.EDx` variant.

quapy/method/non_aggregative.py

@@ -174,8 +174,9 @@ class EDx(_EnergyDistanceCore, BaseQuantifier):
     energy-distance quadratic program directly in feature space.
 
     This implementation works for binary and multiclass single-label
-    quantification and relies on the optional ``quadprog`` dependency. The
-    current QuaPy adaptation shares its numerical core with EDy and keeps
+    quantification and relies on the ``quadprog`` package for solving the
+    underlying quadratic program. The current QuaPy adaptation shares its
+    numerical core with EDy and keeps
     credit to the original implementation available in
     `quantificationlib <https://github.com/AICGijon/quantificationlib>`_.
 
@@ -226,6 +227,69 @@ class EDx(_EnergyDistanceCore, BaseQuantifier):
         return self._predict_energy(X)
 
 
+class DFMrff(BaseQuantifier):
+    """
+    Distribution Feature Matching with Random Fourier Features (DFM-RFF), a covariate-space
+    distribution-matching quantifier proposed by:
+
+    `Dussap, B., Blanchard, G., & Chérief-Abdellatif, B. E. (2023). Label shift quantification
+    with robustness guarantees via distribution feature matching. In Joint European Conference
+    on Machine Learning and Knowledge Discovery in Databases (pp. 69-85). Springer.
+    <https://doi.org/10.1007/978-3-031-43412-9_5>`_
+
+    The method matches training and test distributions in feature space through a kernel
+    embedding, approximated via random Fourier features for computational efficiency; the authors
+    report this to be the best-performing variant among the kernels they study, which is why it is
+    the one exposed here as a named, public method. Other kernel choices (energy, Gaussian,
+    Laplacian), as well as arbitrary re-combinations of losses and feature representations, remain
+    accessible through the more general :class:`quapy.method.composable.ComposableQuantifier`;
+    this class is a thin convenience wrapper that pins the kernel of
+    :class:`quapy.method.composable.QUnfoldWrapper`-wrapped ``qunfold.KMM`` to ``'rff'``.
+
+    This implementation delegates to the optional `qunfold <https://github.com/mirkobunse/qunfold>`_
+    package (the same backend used by :mod:`quapy.method.composable`); see the "Composable Methods"
+    manual for installation instructions.
+
+    :param sigma: smoothing parameter of the random Fourier feature kernel approximation (default 1)
+    :param n_rff: number of random Fourier features (default 1000)
+    :param solver: the `method` argument passed to `scipy.optimize.minimize` (default 'trust-ncg')
+    :param solver_options: dict of options passed to `scipy.optimize.minimize`; if None (default),
+        `{'gtol': 1e-8, 'maxiter': 1000}` is used
+    :param seed: seed controlling the random Fourier features and the solver (default None)
+    """
+
+    def __init__(self, sigma=1, n_rff=1000, solver='trust-ncg', solver_options=None, seed=None):
+        # imported here (rather than at the top of this module) so that quapy.method.non_aggregative
+        # remains importable without qunfold installed; this import raises a clear, actionable
+        # ImportError (with installation instructions) if qunfold is missing
+        from quapy.method.composable import QUnfoldWrapper  # noqa: F401
+        self.sigma = sigma
+        self.n_rff = n_rff
+        self.solver = solver
+        self.solver_options = solver_options
+        self.seed = seed
+
+    def _build_method(self):
+        import qunfold
+        from quapy.method.composable import QUnfoldWrapper
+        solver_options = self.solver_options if self.solver_options is not None else {'gtol': 1e-8, 'maxiter': 1000}
+        return QUnfoldWrapper(qunfold.KMM(
+            kernel='rff', sigma=self.sigma, n_rff=self.n_rff,
+            solver=self.solver, solver_options=solver_options, seed=self.seed,
+        ))
+
+    def fit(self, X, y):
+        self._method = self._build_method()
+        self._method.fit(X, y)
+        return self
+
+    def predict(self, X):
+        return self._method.predict(X)
+
+    def __str__(self):
+        return f'{self.__class__.__name__}(sigma={self.sigma}, n_rff={self.n_rff})'
+
+
 class ReadMe(BaseQuantifier, WithConfidenceABC):
     """
     ReadMe is a non-aggregative quantification system proposed by

quapy/tests/test_methods.py

@@ -7,7 +7,7 @@ import numpy as np
 from sklearn.linear_model import LogisticRegression
 
 from quapy.method import AGGREGATIVE_METHODS, BINARY_METHODS, NON_AGGREGATIVE_METHODS
-from quapy.method.non_aggregative import DMx, EDx, HDx
+from quapy.method.non_aggregative import DFMrff, DMx, EDx, HDx
 from quapy.method.aggregative import ACC, BBSEhard, BBSEsoft, DMy, EDy, KDEyCS, LEIP, RLLS
 from quapy.method.meta import Ensemble
 from quapy.functional import check_prevalence_vector
@@ -20,12 +20,11 @@ OPTIONAL_AGGREGATIVE_METHODS = {
     'BayesianMAPLS',
     'PQ',
     'RLLS',
-    'EDy',
     'LEIP',
 }
 
 OPTIONAL_NON_AGGREGATIVE_METHODS = {
-    'EDx',
+    'DFMrff',
 }
 
 
@@ -235,26 +234,27 @@ class TestMethods(unittest.TestCase):
                 self.assertTrue(check_prevalence_vector(estim_prevalences))
 
     def test_edy(self):
-        try:
-            import quadprog  # noqa: F401
-        except ImportError:
-            return
-
         dataset = TestMethods.tiny_dataset_multiclass
         q = EDy(LogisticRegression(max_iter=2000), val_split=3)
         q.fit(*dataset.training.Xy)
         estim_prevalences = q.predict(dataset.test.X)
         self.assertTrue(check_prevalence_vector(estim_prevalences))
 
-
     def test_edx(self):
+        dataset = TestMethods.tiny_dataset_multiclass
+        q = EDx()
+        q.fit(*dataset.training.Xy)
+        estim_prevalences = q.predict(dataset.test.X)
+        self.assertTrue(check_prevalence_vector(estim_prevalences))
+
+    def test_dfmrff(self):
         try:
-            import quadprog  # noqa: F401
+            import qunfold  # noqa: F401
         except ImportError:
             return
 
         dataset = TestMethods.tiny_dataset_multiclass
-        q = EDx()
+        q = DFMrff(n_rff=50)
         q.fit(*dataset.training.Xy)
         estim_prevalences = q.predict(dataset.test.X)
         self.assertTrue(check_prevalence_vector(estim_prevalences))

setup.py

@@ -89,7 +89,6 @@ setup(
         'License :: OSI Approved :: BSD License',
 
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3 :: Only',
     ],
@@ -117,9 +116,9 @@ setup(
         'quapy.method': ['stan/*.stan']
     },
 
-    python_requires='>=3.8, <4',
+    python_requires='>=3.9, <4',
 
-    install_requires=['scikit-learn', 'pandas', 'tqdm', 'matplotlib', 'joblib', 'xlrd', 'abstention', 'ucimlrepo', 'certifi'],
+    install_requires=['scikit-learn', 'pandas', 'tqdm', 'matplotlib', 'joblib', 'xlrd', 'abstention', 'ucimlrepo', 'certifi', 'quadprog'],
 
     # List additional groups of dependencies here (e.g. development
     # dependencies). Users will be able to install these using the "extras"