code: def test_ricker(self):
      w = wavelets.ricker(1.0, 1)
      expected = 2 / (np.sqrt(3 * 1.0) * (np.pi**0.25))
      assert_array_equal(w, expected)
  
      lengths = [5, 11, 15, 51, 101]
      for length in lengths:
          w = wavelets.ricker(length, 1.0)
          assert_(len(w) == length)
          max_loc = np.argmax(w)
          assert_(max_loc == (length // 2))
  
      points = 100
      w = wavelets.ricker(points, 2.0)
      half_vec = np.arange(0, points // 2)
      # Wavelet should be symmetric
      assert_array_almost_equal(w[half_vec], w[-(half_vec + 1)])
  
      # Check zeros
      aas = [5, 10, 15, 20, 30]
      points = 99
      for a in aas:
          w = wavelets.ricker(points, a)
          vec = np.arange(0, points) - (points - 1.0) / 2
          exp_zero1 = np.argmin(np.abs(vec - a))
          exp_zero2 = np.argmin(np.abs(vec + a))
          assert_array_almost_equal(w[exp_zero1], 0)
          assert_array_almost_equal(w[exp_zero2], 0)
  
file_path: catboost/contrib/python/scipy/py3/scipy/signal/tests/test_wavelets.py
imports: import numpy
  from numpy.testing import assert_equal, assert_array_equal, assert_array_almost_equal, assert_array_less, assert_
  from scipy.signal import wavelets
label_desc: Use image node_id 6 for calling the TestWavelets obj's underlying member method code with example usage: obj.test_ricker() without return types