dcfft.pro

NRAO GBTIDL
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SUMMARY: fields | routine DETAILS: routine

./toolbox
dcfft.pro

Last modification date:: Wed Sep 28 13:27:10 2016

dcfft

function dcfft(real[, imag], [/inverse], [bdrop=integer], [edrop=integer])

Do an FFT (forward or inverse) of a data container. For a real-to-complex FFT, only one data container is given in the arguments. For a complex-to-complex FFT, the real part comes from the first data container and the imaginary part comes from the second data container. The returned value is always a complex array containing the results of the FFT. The input data containers are not changed by this function. It is up to the caller to determine what to do with this result (e.g. further calculations, store the real part in one data container and the imaginary part in another, etc).

This uses the builtin IDL FFT function.

For spectral-line data, when inverse is not set (the default) the builtin IDL inverse flag is used. This means that when dcfft is called with its default arguments and the input data container is a spectrum, the IDL FFT will convert properly from the frequency domain to the time domain (which is actually an inverse FFT). When inverse is set, the builtin IDL inverse flag is not set. This may be confusing to IDL users, but it will be familiar to former UniPOPS users.

For continuum data, the inverse flag here is exactly the same as the inverse flag in the builtin IDL function.

Returns: A complex array containing the result of the FFT. Returns -1 if no data was found in the real argument.
Version: $Id$

Parameters

real
in, required
data container The real part of the data to be FFTed.

imag
in, optional
data container The imaginary part of the data to be FFTed. When not supplied, it is assumed that the data are pure real (imaginary part is all zero).

Keywords

inverse
in, optional
boolean When set, the inverse of the regular FFT is done. For spectral-line data, an inverse FFT is done when this is not set and a direct FFT is done when this is set so that the non-inverse transformation as seen by the dcfft user is frequency to time and the inverse transformation is time to frequency.

bdrop
in, optional
integer (def. 0) The number of channels to exclude from the FFT at the beginning.

edrop
in, optional
integer (def. 0) The number of channels to exclude from the FFT at the end.

Produced by IDLdoc 1.6 on Wed Sep 28 13:27:38 2016

Parameters
real in, required data container	The real part of the data to be FFTed.
imag in, optional data container	The imaginary part of the data to be FFTed. When not supplied, it is assumed that the data are pure real (imaginary part is all zero).

Keywords
inverse in, optional boolean	When set, the inverse of the regular FFT is done. For spectral-line data, an inverse FFT is done when this is not set and a direct FFT is done when this is set so that the non-inverse transformation as seen by the dcfft user is frequency to time and the inverse transformation is time to frequency.
bdrop in, optional integer (def. 0)	The number of channels to exclude from the FFT at the beginning.
edrop in, optional integer (def. 0)	The number of channels to exclude from the FFT at the end.