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Справка Scilab >> Signal Processing > Transforms > ifftshift

# ifftshift

inverse of fftshift

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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