++ Authored by: Kevin Murphy & Zhark the Transformer 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.
- -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 = Dec 16 2015
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