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# scipy.fftpack.ss_diff

`scipy.fftpack.``ss_diff`(x, a, b, period=None, _cache={})

  Return (a,b)-sinh/sinh pseudo-derivative of a periodic sequence x.

  If x_j and y_j are Fourier coefficients of periodic functions x and y, respectively, then:

      y_j = sinh(j*a*2*pi/period)/sinh(j*b*2*pi/period) * x_j
      y_0 = a/b * x_0

  Parameters: | x : array_like The array to take the pseudo-derivative from. a,b Defines the parameters of the sinh/sinh pseudo-differential operator. period : float, optional The period of the sequence x. Default is `2*pi`.

  Notes

  `ss_diff(ss_diff(x,a,b),b,a) == x`