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# scipy.signal.savgol_coeffs

`scipy.signal.``savgol_coeffs`(window_length, polyorder, deriv=0, delta=1.0, pos=None, use='conv')

  Compute the coefficients for a 1-d Savitzky-Golay FIR filter.

  Parameters:

  window_length : int

  > The length of the filter window (i.e. the number of coefficients). window_length must be an odd positive integer.

  polyorder : int

  > The order of the polynomial used to fit the samples. polyorder must be less than window_length.

  deriv : int, optional

  > The order of the derivative to compute. This must be a nonnegative integer. The default is 0, which means to filter the data without differentiating.

  delta : float, optional

  > The spacing of the samples to which the filter will be applied. This is only used if deriv > 0.

  pos : int or None, optional

  > If pos is not None, it specifies evaluation position within the window. The default is the middle of the window.

  use : str, optional

  > Either ‘conv’ or ‘dot’. This argument chooses the order of the coefficients. The default is ‘conv’, which means that the coefficients are ordered to be used in a convolution. With use=’dot’, the order is reversed, so the filter is applied by dotting the coefficients with the data set.

  Returns:

  coeffs : 1-d ndarray

  > The filter coefficients.

  See also

  `savgol_filter`

  Notes

  New in version 0.14.0.

  References

  A. Savitzky, M. J. E. Golay, Smoothing and Differentiation of Data by Simplified Least Squares Procedures. Analytical Chemistry, 1964, 36 (8), pp 1627-1639.

  Examples

      >>> from scipy.signal import savgol_coeffs
      >>> savgol_coeffs(5, 2)
      array([-0.08571429,  0.34285714,  0.48571429,  0.34285714, -0.08571429])
      >>> savgol_coeffs(5, 2, deriv=1)
      array([  2.00000000e-01,   1.00000000e-01,   2.00607895e-16,
              -1.00000000e-01,  -2.00000000e-01])

  Note that use=’dot’ simply reverses the coefficients.

      >>> savgol_coeffs(5, 2, pos=3)
      array([ 0.25714286,  0.37142857,  0.34285714,  0.17142857, -0.14285714])
      >>> savgol_coeffs(5, 2, pos=3, use='dot')
      array([-0.14285714,  0.17142857,  0.34285714,  0.37142857,  0.25714286])

  x contains data from the parabola x = t**2, sampled at t = -1, 0, 1, 2, 3. c holds the coefficients that will compute the derivative at the last position. When dotted with x the result should be 6.

      >>> x = np.array([1, 0, 1, 4, 9])
      >>> c = savgol_coeffs(5, 2, pos=4, deriv=1, use='dot')
      >>> c.dot(x)
      6.0000000000000018