Programmer Guide/Command Reference/EVAL/dft

Inverse or forward discrete fourier transform (dft).

Usage

dft(x {, type)

xthe data vector to be transformed

type

selects the data type of the argument and result and the transformation to be performed (default=0)

Result

A vector y containing the result of the transformation. The length and content of y depends on x and type.

type	x	nrow(x)	y	nrow(y)	description
0	real signal with N samples	N	complex spectrum with N/2+1 values	N+2	forward real->complex dft note: only the first half (values: 0..N/2) of the conj. sym. complex spectrum is stored in y
1	complex signal with N samples	2N	complex spectrum with N values	2N	forward complex->complex dft
2	first half (values: 0..N/2) of a conj. sym. complex spectrum	N+2	real signal with N samples	N	inverse complex->real dft note: this is the inverse of type=0
3	complex spectrum with N values	2N	complex signal with N samples	2N	inverse complex->complex dft

See also

fft, ifft, dct, cepstrum, lpc, complex arithmetic

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