3dDFT

Contents

• 3dDFT

Usage: 3dDFT [options] dataset
       where 'dataset' is complex- or float-valued.
 * Carries out the DFT along the time axis.
 * To do the DFT along the spatial axes, use program 3dFFT.
 * The input dataset can be complex-valued or float-valued.
   If it is any other data type, it will be converted to floats
   before processing.

OPTIONS:
--------
 -abs     == output float dataset = abs(DFT)
            * Otherwise, the output file is complex-valued.
              You can then use 3dcalc to extract the real part, the
              imaginary part, the phase, etc.; see its '-cx2r' option:
                3dcalc  -cx2r REAL -a cxset+orig-expr a -prefix rset+orig
            * Please note that if you view a complex dataset in AFNI,
              the default operation is that you are looking at the
              absolute value of the dataset.
             ++ You can control the way a complex IMAGE appears via
                the 'Disp' control panel (ABS, PHASE, REAL, IMAGE).
             ++ You can control the way a complex TIME SERIES graph appears
                via environment variable AFNI_GRAPH_CX2R (in 'EditEnv').

 -nfft N  == use 'N' for DFT length (must be >= #time points)

 -detrend == least-squares remove linear drift before DFT
              [for more intricate detrending, use 3dDetrend first]

 -taper f == taper 'f' fraction of data at ends (0 <= f <= 1).
              [Hamming 'raised cosine' taper of f/2 of the ]
              [data length at each end; default is no taper]
              [cf. 3dPeriodogam -help for tapering details!]

 -inverse == Do the inverse DFT:
               SUM{ data[j] * exp(+2*PI*i*j/nfft) } * 1/nfft
             instead of the forward transform
               SUM{ data[j] * exp(-2*PI*i*j/nfft) }

++ Compile date = Mar 27 2018 {AFNI_18.0.27:linux_ubuntu_16_64}