ifft function

ArrayComplex ifft(
  1. ArrayComplex X
)

Compute the one-dimensional inverse discrete Fourier Transform.

  • X An ArrayComplex with the input return An ArrayComplex with IFFT output

References

  1. "Fast Fourier Transform". // https://rosettacode.org/wiki/Fast_Fourier_transform#C++. Retrieved 2019-07-23.

Examples

var X = ArrayComplex([
  Complex(real: 4.0, imaginary: 0.0),
  Complex(real: 1.0, imaginary: -2.41421356),
  Complex(real: 0.0, imaginary: 0.0),
  Complex(real: 1.0, imaginary: -0.41421356),
  Complex(real: 0.0, imaginary: 0.0),
  Complex(real: 1.0, imaginary: 0.41421356),
  Complex(real: 0.0, imaginary: 0.0),
  Complex(real: 1.0, imaginary: 2.41421356)
]);

print(ifft(X));

/* output:
ArrayComplex([
  Complex(real: 1.00000000e+00, imaginary: 0.00000000e+00),
  Complex(real: 9.99999999e-01, imaginary: -5.55111512e-17),
  Complex(real: 1.00000000e+00, imaginary: 0.00000000e+00),
  Complex(real: 9.99999999e-01, imaginary: -5.55111512e-17),
  Complex(real: 0.00000000e+00, imaginary: 0.00000000e+00),
  Complex(real: 8.39015857e-10, imaginary: 5.55111512e-17),
  Complex(real: 0.00000000e+00, imaginary: 0.00000000e+00),
  Complex(real: 8.39015857e-10, imaginary: 5.55111512e-17)
])
*/

Implementation

ArrayComplex ifft(ArrayComplex X) {
  // conjugate the complex numbers
  var XConj = arrayComplexConjugate(X);

  // forward fft
  var xImag = fft(XConj);

  // conjugate the complex numbers again
  xImag = arrayComplexConjugate(xImag);

  // scale the numbers
  xImag = arrayComplexDivisionToScalar(xImag, xImag.length);

  return xImag;
}