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Справка Scilab >> Signal Processing > ifftshift

ifftshift

inverse of fftshift

Calling Sequence

y=ifftshift(x)

Arguments

x, y

real or complex vector or matrix.

Description

ifftshift(x) swaps the left and right halves of the vector x.

For matrices, ifftshift(x) swaps the first quadrant with the third and the second quadrant with the fourth.

If x is a multidimensional array, ifftshift(x) swaps "half-spaces" of x along each dimension.

Examples

Example #1:

// Make a signal
t = 0:0.1:1000;
x = 3*sin(t)+8*sin(3*t)+0.5*sin(5*t)+3*rand(t);
// Compute the fft
y = fft(x, -1);
// Invert the result
shift = fftshift(y);
// Invert the inverted result
invShift = ifftshift(shift);
// Check that we recreated the original result
and(y == invShift)

Example #2:

// Make a 2D image
t = 0:0.1:30;
x = 3*sin(t')*cos(2*t)+8*sin(3*t')*sin(5*t)+..
  0.5*sin(5*t')*sin(5*t)+3*rand(t')*rand(t);
// Compute the fft
y = fft(x,-1);

// Invert the result
shift = fftshift(y);
// Invert the inverted result
invShift = ifftshift(shift);
// Check that we recreated the original result
and(y == invShift)

See Also

  • fftshift — rearranges the fft output, moving the zero frequency to the center of the spectrum
  • fft — fast Fourier transform.
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Last updated:
Thu Oct 02 14:01:06 CEST 2014