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# scipy.special.ynp_zeros

scipy.special.ynp_zeros(n, nt)

  Compute zeros of integer-order Bessel function derivatives Yn’(x).

  Compute nt zeros of the functions \(Y_n'(x)\) on the interval \((0, \infty)\). The zeros are returned in ascending order.

  Parameters:
    n int

      Order of Bessel function

    nt int

      Number of zeros to return

  Returns:
    ndarray

      First nt zeros of the Bessel derivative function.

  See also

  `yvp`

  References

  [1]

  Zhang, Shanjie and Jin, Jianming. “Computation of Special Functions”, John Wiley and Sons, 1996, chapter 5. https://people.sc.fsu.edu/~jburkardt/f77_src/special_functions/special_functions.html

  Examples

  Compute the first four roots of the first derivative of the Bessel function of second kind for order 0 \(Y_0'\).

      >>> from scipy.special import ynp_zeros
      >>> ynp_zeros(0, 4)
      array([ 2.19714133,  5.42968104,  8.59600587, 11.74915483])

  Plot \(Y_0\), \(Y_0'\) and confirm visually that the roots of \(Y_0'\) are located at local extrema of \(Y_0\).

      >>> import numpy as np
      >>> import matplotlib.pyplot as plt
      >>> from scipy.special import yn, ynp_zeros, yvp
      >>> zeros = ynp_zeros(0, 4)
      >>> xmax = 13
      >>> x = np.linspace(0, xmax, 500)
      >>> fig, ax = plt.subplots()
      >>> ax.plot(x, yn(0, x), label=r'$Y_0$')
      >>> ax.plot(x, yvp(0, x, 1), label=r"$Y_0'$")
      >>> ax.scatter(zeros, np.zeros((4, )), s=30, c='r',
      ...            label=r"Roots of $Y_0'$", zorder=5)
      >>> for root in zeros:
      ...     y0_extremum =  yn(0, root)
      ...     lower = min(0, y0_extremum)
      ...     upper = max(0, y0_extremum)
      ...     ax.vlines(root, lower, upper, color='r')
      >>> ax.hlines(0, 0, xmax, color='k')
      >>> ax.set_ylim(-0.6, 0.6)
      >>> ax.set_xlim(0, xmax)
      >>> plt.legend()
      >>> plt.show()