text: from sklearn.utils.testing import assert_true
  import numpy as np
  import scipy.sparse as sp
  
  from sklearn.utils.testing import assert_less
  from sklearn.utils.testing import assert_greater
  from sklearn.utils.testing import assert_array_almost_equal, assert_array_equal
  from sklearn.utils.testing import assert_almost_equal
  from sklearn.utils.testing import assert_raises
  
  from sklearn.base import ClassifierMixin
  from sklearn.utils import check_random_state
  from sklearn.datasets import load_iris
  from sklearn.linear_model import PassiveAggressiveClassifier
  from sklearn.linear_model import PassiveAggressiveRegressor
  
  iris = load_iris()
  random_state = check_random_state(12)
  indices = np.arange(iris.data.shape[0])
  random_state.shuffle(indices)
  X = iris.data[indices]
  y = iris.target[indices]
  X_csr = sp.csr_matrix(X)
  
  
  class MyPassiveAggressive(ClassifierMixin):
  
      def __init__(self, C=1.0, epsilon=0.01, loss="hinge",
                   fit_intercept=True, n_iter=1, random_state=None):
          self.C = C
          self.epsilon = epsilon
          self.loss = loss
          self.fit_intercept = fit_intercept
          self.n_iter = n_iter
  
      def fit(self, X, y):
          n_samples, n_features = X.shape
          self.w = np.zeros(n_features, dtype=np.float64)
          self.b = 0.0
  
          for t in range(self.n_iter):
              for i in range(n_samples):
                  p = self.project(X[i])
                  if self.loss in ("hinge", "squared_hinge"):
                      loss = max(1 - y[i] * p, 0)
                  else:
                      loss = max(np.abs(p - y[i]) - self.epsilon, 0)
  
                  sqnorm = np.dot(X[i], X[i])
  
                  if self.loss in ("hinge", "epsilon_insensitive"):
                      step = min(self.C, loss / sqnorm)
                  elif self.loss in ("squared_hinge",
                                     "squared_epsilon_insensitive"):
                      step = loss / (sqnorm + 1.0 / (2 * self.C))
  
                  if self.loss in ("hinge", "squared_hinge"):
                      step *= y[i]
                  else:
                      step *= np.sign(y[i] - p)
  
                  self.w += step * X[i]
                  if self.fit_intercept:
                      self.b += step
  
      def project(self, X):
          return np.dot(X, self.w) + self.b
  
  
  def test_classifier_accuracy():
      for data in (X, X_csr):
          for fit_intercept in (True, False):
              for average in (False, True):
                  clf = PassiveAggressiveClassifier(
                      C=1.0, max_iter=30, fit_intercept=fit_intercept,
                      random_state=0, average=average, tol=None)
                  clf.fit(data, y)
                  score = clf.score(data, y)
                  assert_greater(score, 0.79)
                  if average:
                      assert_true(hasattr(clf, 'average_coef_'))
                      assert_true(hasattr(clf, 'average_intercept_'))
                      assert_true(hasattr(clf, 'standard_intercept_'))
                      assert_true(hasattr(clf, 'standard_coef_'))
  
  
  def test_classifier_partial_fit():
      classes = np.unique(y)
      for data in (X, X_csr):
          for average in (False, True):
              clf = PassiveAggressiveClassifier(
                  C=1.0, fit_intercept=True, random_state=0,
                  average=average, max_iter=5)
              for t in range(30):
                  clf.partial_fit(data, y, classes)
              score = clf.score(data, y)
              assert_greater(score, 0.79)
              if average:
                  assert_true(hasattr(clf, 'average_coef_'))
                  assert_true(hasattr(clf, 'average_intercept_'))
                  assert_true(hasattr(clf, 'standard_intercept_'))
                  assert_true(hasattr(clf, 'standard_coef_'))
  
  
  def test_classifier_refit():
      # Classifier can be retrained on different labels and features.
      clf = PassiveAggressiveClassifier(max_iter=5).fit(X, y)
      assert_array_equal(clf.classes_, np.unique(y))
  
      clf.fit(X[:, :-1], iris.target_names[y])
      assert_array_equal(clf.classes_, iris.target_names)
  
  
  def test_classifier_correctness():
      y_bin = y.copy()
      y_bin[y != 1] = -1
  
      for loss in ("hinge", "squared_hinge"):
  
          clf1 = MyPassiveAggressive(
              C=1.0, loss=loss, fit_intercept=True, n_iter=2)
          clf1.fit(X, y_bin)
  
          for data in (X, X_csr):
              clf2 = PassiveAggressiveClassifier(
                  C=1.0, loss=loss, fit_intercept=True, max_iter=2,
                  shuffle=False, tol=None)
              clf2.fit(data, y_bin)
  
              assert_array_almost_equal(clf1.w, clf2.coef_.ravel(), decimal=2)
  
  
  def test_classifier_undefined_methods():
      clf = PassiveAggressiveClassifier(max_iter=100)
      for meth in ("predict_proba", "predict_log_proba", "transform"):
          assert_raises(AttributeError, lambda x: getattr(clf, x), meth)
  
  
  def test_class_weights():
      # Test class weights.
      X2 = np.array([[-1.0, -1.0], [-1.0, 0], [-.8, -1.0],
                     [1.0, 1.0], [1.0, 0.0]])
      y2 = [1, 1, 1, -1, -1]
  
      clf = PassiveAggressiveClassifier(C=0.1, max_iter=100, class_weight=None,
                                        random_state=100)
      clf.fit(X2, y2)
      assert_array_equal(clf.predict([[0.2, -1.0]]), np.array([1]))
  
      # we give a small weights to class 1
      clf = PassiveAggressiveClassifier(C=0.1, max_iter=100,
                                        class_weight={1: 0.001},
                                        random_state=100)
      clf.fit(X2, y2)
  
      # now the hyperplane should rotate clock-wise and
      # the prediction on this point should shift
      assert_array_equal(clf.predict([[0.2, -1.0]]), np.array([-1]))
  
  
  def test_partial_fit_weight_class_balanced():
      # partial_fit with class_weight='balanced' not supported
      clf = PassiveAggressiveClassifier(class_weight="balanced", max_iter=100)
      assert_raises(ValueError, clf.partial_fit, X, y, classes=np.unique(y))
  
  
  def test_equal_class_weight():
      X2 = [[1, 0], [1, 0], [0, 1], [0, 1]]
      y2 = [0, 0, 1, 1]
      clf = PassiveAggressiveClassifier(
          C=0.1, max_iter=1000, tol=None, class_weight=None)
      clf.fit(X2, y2)
  
      # Already balanced, so "balanced" weights should have no effect
      clf_balanced = PassiveAggressiveClassifier(
          C=0.1, max_iter=1000, tol=None, class_weight="balanced")
      clf_balanced.fit(X2, y2)
  
      clf_weighted = PassiveAggressiveClassifier(
          C=0.1, max_iter=1000, tol=None, class_weight={0: 0.5, 1: 0.5})
      clf_weighted.fit(X2, y2)
  
      # should be similar up to some epsilon due to learning rate schedule
      assert_almost_equal(clf.coef_, clf_weighted.coef_, decimal=2)
      assert_almost_equal(clf.coef_, clf_balanced.coef_, decimal=2)
  
  
  def test_wrong_class_weight_label():
      # ValueError due to wrong class_weight label.
      X2 = np.array([[-1.0, -1.0], [-1.0, 0], [-.8, -1.0],
                     [1.0, 1.0], [1.0, 0.0]])
      y2 = [1, 1, 1, -1, -1]
  
      clf = PassiveAggressiveClassifier(class_weight={0: 0.5}, max_iter=100)
      assert_raises(ValueError, clf.fit, X2, y2)
  
  
  def test_wrong_class_weight_format():
      # ValueError due to wrong class_weight argument type.
      X2 = np.array([[-1.0, -1.0], [-1.0, 0], [-.8, -1.0],
                     [1.0, 1.0], [1.0, 0.0]])
      y2 = [1, 1, 1, -1, -1]
  
      clf = PassiveAggressiveClassifier(class_weight=[0.5], max_iter=100)
      assert_raises(ValueError, clf.fit, X2, y2)
  
      clf = PassiveAggressiveClassifier(class_weight="the larch", max_iter=100)
      assert_raises(ValueError, clf.fit, X2, y2)
  
  
  def test_regressor_mse():
      y_bin = y.copy()
      y_bin[y != 1] = -1
  
      for data in (X, X_csr):
          for fit_intercept in (True, False):
              for average in (False, True):
                  reg = PassiveAggressiveRegressor(
                      C=1.0, fit_intercept=fit_intercept,
                      random_state=0, average=average, max_iter=5)
                  reg.fit(data, y_bin)
                  pred = reg.predict(data)
                  assert_less(np.mean((pred - y_bin) ** 2), 1.7)
                  if average:
                      assert_true(hasattr(reg, 'average_coef_'))
                      assert_true(hasattr(reg, 'average_intercept_'))
                      assert_true(hasattr(reg, 'standard_intercept_'))
                      assert_true(hasattr(reg, 'standard_coef_'))
  
  
  def test_regressor_partial_fit():
      y_bin = y.copy()
      y_bin[y != 1] = -1
  
      for data in (X, X_csr):
          for average in (False, True):
              reg = PassiveAggressiveRegressor(
                  C=1.0, fit_intercept=True, random_state=0,
                  average=average, max_iter=100)
              for t in range(50):
                  reg.partial_fit(data, y_bin)
              pred = reg.predict(data)
              assert_less(np.mean((pred - y_bin) ** 2), 1.7)
              if average:
                  assert_true(hasattr(reg, 'average_coef_'))
                  assert_true(hasattr(reg, 'average_intercept_'))
                  assert_true(hasattr(reg, 'standard_intercept_'))
                  assert_true(hasattr(reg, 'standard_coef_'))
  
  
  def test_regressor_correctness():
      y_bin = y.copy()
      y_bin[y != 1] = -1
  
      for loss in ("epsilon_insensitive", "squared_epsilon_insensitive"):
          reg1 = MyPassiveAggressive(
              C=1.0, loss=loss, fit_intercept=True, n_iter=2)
          reg1.fit(X, y_bin)
  
          for data in (X, X_csr):
              reg2 = PassiveAggressiveRegressor(
                  C=1.0, tol=None, loss=loss, fit_intercept=True, max_iter=2,
                  shuffle=False)
              reg2.fit(data, y_bin)
  
              assert_array_almost_equal(reg1.w, reg2.coef_.ravel(), decimal=2)
  
  
  def test_regressor_undefined_methods():
      reg = PassiveAggressiveRegressor(max_iter=100)
      for meth in ("transform",):
          assert_raises(AttributeError, lambda x: getattr(reg, x), meth)
  