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fft

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• name:
  fft
• synopsis:

  fft inputfile outputfile [-full_output= filename] [-window[={hanning | welch | parzen}]] [-pad_with_zeroes | -truncate] [-sample_interval= integer] [-suppress_average] [-normalize] [-log_output] [-low_pass= frequency] [-high_pass= frequency] [-use_omega] [-single_precision]

• description:
  Performs the FFT of a data set, producing a new data set with the magnitude vs. the frequency. Also does optional windowing[4] and provides output of real and imaginary components. Will work in either single or double precision, and will optionally pad or truncate a data set to achieve data points (necessary for the FFT).
• files:
  inputfile contains the input data set, which must have points at equispaced abscissae. The magnitude vs frequency of the FFT of the input data set is placed outputfile.
• options:

  full_output

  
  Requests fft to provide complete output of the FFT, which includes the real and imaginary parts, the magnitudes, and the phases.

  window

  
  Specifies windowing of the data prior to taking the FFT.

  pad_with_zeroes, truncate

  
  These options provide two alternative ways of dealing with data sets that do not have points. pad_with_zeroes causes the data set to be lengthened to the smallest power of 2 not less than the number of data points, while truncate causes the data set to be truncated to the largest power of 2 not greater than the number of data points.

  sample_interval

  
  Specifies a sampling interval for reducing the number of data points processed by using only every point from the data set.

  suppress_average

  
  Requests that the average data value be subtracted from all data values prior to taking the FFT.

  normalize

  
  Requests normalization of the frequency spectrum so that the largest magnitude is unity.

  log_output

  
  Requests output of the base-ten logarithm of the magnitude.

  low_pass

  
  Requests output only at or below the specified frequency.

  high_pass

  
  Requests output only at or above the specified frequency.

  use_omega

  
  Requests use of angular frequency in the output files.

  single_precision

  
  Requests use of single-precision arithmetic in performing all operations.

• see also:

  
  filter.