ReFFT
Advanced Analysis Library Only
AnalysisLibErrType ReFFT (double arrayXReal[], double arrayXImaginary[], ssize_t numberOfElements);
Purpose
 |
Note This function has been superseded by FFTEx. FFTEx includes additional parameters, which makes it more versatile than ReFFT. |
Calculates the fast Fourier transform (FFT) of a real input array.
ReFFT performs the operation in place and overwrites the input array. Performing an FFT on a real array yields a complex result. The imaginary component array must be at least as large as the real component array.
The following example illustrates the form of the output arrays, with numberOfElements being the output signal length.
If numberOfElements is even, arrayXReal and arrayXImg have the following form:
[ DC component, f[1], f[2], f[3], f[4].....f[nyquist-1], f[nyquist],-f[nyquist-1] ...-f[4], -f[3], -f[2], -f[1] ]
If numberOfElements is odd, arrayXReal and arrayXImg have the following form:
[ DC component, f[1], f[2], f[3], f[4].....f[(n-1)/2], -f[(n-1)/2] ...-f[4], -f[3], -f[2], -f[1] ]
Example Code
/* Generate an array with random numbers and calculate the fast Fourier transform. */
double x[256], y[256];
n;
n = 256;
Uniform (n, x);
ReFFT (x, y, n);
Parameters
| Input | ||
| Name | Type | Description |
| numberOfElements | ssize_t | Number of elements in the input arrays. |
| Output | ||
| Name | Type | Description |
| arrayX_Real | double [] | On input, the real part of the array used to compute the FFT. arrayXReal must satisfy arrayXReal[i] = arrayXReal[numberOfElements–i], i = 1, 2, …, numberOfElements–1. On output, the real part of the FFT. This operation is performed in place, meaning the values in this array are overwritten. |
| arrayX_Imaginary | double [] | On input, the values are ignored. On output, the imaginary part of the FFT. This operation is performed in place, meaning the values in this array are overwritten. |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 3.1 and later
Examples
Refer to the following examples that use the ReFFT function:
- analysis\2dfft.cws
Open example - analysis\convolve.cws
Open example - analysis\iirfiltr.cws
Open example - OpenMP\2dfft_omp.cws
Open example