7.1.17. 1dfftΒΆ

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Usage: 1dfft [options] infile outfile where infile is an AFNI *.1D file (ASCII list of numbers arranged in columns); outfile will be a similar file, with the absolute value of the FFT of the input columns. The length of the file will be 1+(FFT length)/2.

Options:

-ignore sss = Skip the first ‘sss’ lines in the input file.
[default = no skipping]
-use uuu = Use only ‘uuu’ lines of the input file.
[default = use them all, Frank]
-nfft nnn = Set FFT length to ‘nnn’.
[default = length of data (# of lines used)]
-tocx = Save Re and Im parts of transform in 2 columns.
-fromcx = Convert 2 column complex input into 1 column
real output.
-hilbert = When -fromcx is used, the inverse FFT will
do the Hilbert transform instead.
-nodetrend = Skip the detrending of the input.
Nota Bene:
  • Each input time series has any quadratic trend of the

    form ‘a+b*t+c*t*t’ removed before the FFT, where ‘t’ is the line number.

  • The FFT length will be a power-of-2 times at most one

    factor of 3 and one factor of 5. The smallest such length >= to the specified FFT length will be used.

  • If the FFT length is longer than the file length, the

    data is zero-padded to make up the difference.

  • Do NOT call the output of this program the Power Spectrum!

    That is something else entirely.

  • If ‘outfile’ is ‘-‘, the output appears on stdout.

++ Compile date = Dec 16 2015

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