Ifft
Discrete inverse Fourier transform.
 
Loading        LOADSUB ALL FROM "FFT.HTS"
or LOADSUB FROM "MATHLIB.HTS"
or LOADSUB Ifft FROM "MATHLIB.HTS"
 
Usage                INTEGER Logn
REAL A(*)
COMPLEX F(*)
CALL Ifft(Logn,F(*),A(*))
 
Description                
Ifft calculates the discrete inverse Fourier transform of the sequence in the array F and stores the result in the array A. Logn is the base-2 log of the number of points in the sequences. The array F must contain at least 2Logn-1 elements; the array A must contain at least 2Logn elements. If the arrays have more than the required number of elements, the extra elements are ignored and unmodified. The number of elements in A denoted by each permitted value of Logn is shown in the table below:
 
Logn                No. Elements (2Logn)
2                4
3                8
4                16
5                32
6                64
7                128
8                256
9                512
10                1024
11                2048
12                4096
13                8192
14                16384
 
 
The values input to Ifft are in the same format as those output by the Fft routine. See the entry for Fft for a detailed explanation of the meaning of the values returned by Ifft.
 
Errors                
Ifft causes an HTBasic error if its arguments are not of the types shown in the USAGE section, above, if Logn is not between 2 and 15, inclusive, or if the size of A or F is smaller than the values explained above.
See Also
Fft, Icfft