code: def window_riemann(N):
      r
      n = linspace(-N/2., (N)/2., N)
      w = sin(n/float(N)*2.*pi) / (n / float(N)*2.*pi)
      return w
docs: r"""Riemann tapering window
  
      :param int N: window length
  
      .. math:: w(n) = 1 - \left| \frac{n}{N/2}  \right|^2
  
      with :math:`-N/2 \leq n \leq N/2`.
  
      .. plot::
          :width: 80%
          :include-source:
  
          from spectrum import window_visu
          window_visu(64, 'riesz')
  
      .. seealso:: :func:`create_window`, :class:`Window`