xrscipy.fftpack.idct

xrscipy.fftpack.idct(x, coord, type=2, n=None, norm=None)

idct(x, coord, type=2, n=None, norm=None)

Parameters:

  • obj (xarray object) – The input array.

  • coord (string) – Coordinate along which the idct is computed. The coordinate must be evenly spaced.

  • type ({1, 2, 3, 4}, optional) – Type of the DCT (see Notes). Default type is 2.

  • n (int, optional) – Length of the transform. If n < x.shape[axis], x is truncated. If n > x.shape[axis], x is zero-padded. The default results in n = x.shape[axis].

  • norm ({None, 'ortho'}, optional) – Normalization mode (see Notes). Default is None.

Returns:

idct – The transformed input array.

Return type:

ndarray of real

See also

dct

Forward DCT

numpy.fftpack.idct

scipy.fft.idct : Original scipy implementation

Notes

For a single dimension array x, idct(x, norm='ortho') is equal to MATLAB idct(x).

‘The’ IDCT is the IDCT of type 2, which is the same as DCT of type 3.

IDCT of type 1 is the DCT of type 1, IDCT of type 2 is the DCT of type 3, and IDCT of type 3 is the DCT of type 2. IDCT of type 4 is the DCT of type 4. For the definition of these types, see dct.

Examples

None The Type 1 DCT is equivalent to the DFT for real, even-symmetrical inputs. The output is also real and even-symmetrical. Half of the IFFT input is used to generate half of the IFFT output:

Examples

>>> from scipy.fftpack import ifft, idct
>>> import numpy as np
>>> ifft(np.array([ 30.,  -8.,   6.,  -2.,   6.,  -8.])).real
array([  4.,   3.,   5.,  10.,   5.,   3.])

Examples

>>> idct(np.array([ 30.,  -8.,   6.,  -2.]), 1) / 6
array([  4.,   3.,   5.,  10.])