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Re: looking for 2D FFT code? [message #7734 is a reply to message #7661]

Fri, 20 December 1996 00:00

jyli
Messages: 21
Registered: November 1995

Junior Member

William Ryu (wsryu@fas2.fas.harvard.edu) wrote:
: While it isn't obvious from the help file, IDL's fft() function will
: do multi-dimensional ffts ("The result returned by FFT is a complex
: array that has the same dimensions as the input array.").

With the help of RSI engineers, I think I have found the answer to my
problem.

In the beginning, I fed a test image into FFT and the resulting power
spectrum was not what I expected. Well now I know it is because the way
IDL stores positive and negative frequency components in the FFT
complex arrays, one needs to do a shift operation before displaying the
spectrum. And now Page 1-280 in the IDL reference manual seems to make
a lot sense.

Thanks for those who have responded.

happy holidays and happy IDL programming !

--

============================================================ ============
Jason Y. Li | Tel : (301) 286-1029
Code 913 | Fax : (301) 286-1759
NASA Goddard Space Flight Center | www : http://climate.gsfc.nasa.gov
Greenbelt, MD 20771, USA | email: jyli@climate.gsfc.nasa.gov
============================================================ ============
Beauty of style, harmony, grace and good rhythm depend on simplicity.

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[Message index]

		looking for 2D FFT code? By: jyli on Tue, 17 December 1996 00:00
		Re: looking for 2D FFT code? By: davidf on Fri, 20 December 1996 00:00
		Re: looking for 2D FFT code? By: jyli on Fri, 20 December 1996 00:00

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