code: def ricker(points, a):
      """
      Return a Ricker wavelet, also known as the "Mexican hat wavelet".
  
      It models the function:
  
          ``A * (1 - (x/a)**2) * exp(-0.5*(x/a)**2)``,
  
      where ``A = 2/(sqrt(3*a)*(pi**0.25))``.
  
      Parameters
      ----------
      points : int
          Number of points in `vector`.
          Will be centered around 0.
      a : scalar
          Width parameter of the wavelet.
  
      Returns
      -------
      vector : (N,) ndarray
          Array of length `points` in shape of ricker curve.
  
      Examples
      --------
      >>> from scipy import signal
      >>> import matplotlib.pyplot as plt
  
      >>> points = 100
      >>> a = 4.0
      >>> vec2 = signal.ricker(points, a)
      >>> print(len(vec2))
      100
      >>> plt.plot(vec2)
      >>> plt.show()
  
      """
      A = 2 / (np.sqrt(3 * a) * (np.pi**0.25))
      wsq = a**2
      vec = np.arange(0, points) - (points - 1.0) / 2
      xsq = vec**2
      mod = 1 - xsq / wsq
      gauss = np.exp(-xsq / (2 * wsq))
      total = A * mod * gauss
      return total
  
file_path: catboost/contrib/python/scipy/py3/scipy/signal/wavelets.py
imports: import numpy
  from scipy.linalg import eig
  from scipy.special import comb
  from scipy.signal import convolve
label_desc: Use image node_id 5 for calling a global function with example usage: ricker(points, a) and returns: total