foutra_usage_help.cc

Go to the documentation of this file.

// DO NOT EDIT: this file is automatically derived from foutra_usage_help.txt
#include "foutra_usage_help.h"
char foutra_usage_help[]=
{
  "foutra applies spectral analysis to time series data. Its primary purpose is\n"
  "the computation of power spectral density (-power). Additionally it offers two\n"
  "other modes of scaling. Values of the Fourier amplitude spectrum can be\n"
  "written to file (-amplitude) as well as values of a spectral representation,\n"
  "where peak values in the spectrum represent amplitudes of harmonic signals\n"
  "present in the time series (-harmonic). If none of these modes is selected, a\n"
  "tapered version of the input time series is written to the output file.\n"
  "\n"
  "Output is written to a file in any of the time series data formats (-Type)\n"
  "supported for output. Samples are then values along increasing frequency,\n"
  "sampling interval is given in Hertz. The first sample in the file is at 0 Hz.\n"
  "The last is the sample at Nyquist frequency.\n"
  "\n"
  "As an option (-ASCII) output to plain ASCII is supported, where the first\n"
  "column in each file specifies frequency in Hertz and the second column\n"
  "specifies the corresponding spectral values. This format supports output with\n"
  "logarithmic sampling along the frequency scale (-logascii).\n"
  "\n"
  "By default (if -power or -harmonic are not selected) foutra computes Fourier\n"
  "amplitude spectra.\n"
  "If input units are K, then the output units of amplitude spectra are K/Hz.\n"
  "\n"
  "Power spectral density\n"
  "----------------------\n"
  "Option: -power\n"
  "\n"
  "Foutra outputs the called the one-sided PSD (power spectral density) 2*P(f),\n"
  "where P(f) is the Fourier transform of the normalized auto-correlation\n"
  "function.\n"
  "\n"
  "If input units are K, then the output units of power spectral density will\n"
  "be K*K/Hz. \n"
  "\n"
  "Option: -scalerbw\n"
  "\n"
  "Option -scalerbw selects the computation of average signal power in a finite\n"
  "relative bandwidth (rather than power spectral density). The square root of\n"
  "this value is rms-amplitude in the finite relative bandwidth. The program\n"
  "however outputs signal power, not rms-amplitude. The units of the output\n"
  "values are K*K.\n"
  "\n"
  "If P(f) is constant in the frequency band f1 to f2, then the rms-amplitude in\n"
  "this band is A=sqrt(2*P(f)*(f2-f1)).\n"
  "\n"
  "The integral over the power spectral density calculated by foutra\n"
  "over the total bandwidth (over all frequencies from 0 Hz to Nyquist\n"
  "frequency) provides the total power of the signal (i.e. the\n"
  "variance of the input signal, i.e. the square of the rms value).\n"
  "This value will be output upon selection of option -rms.\n"
  "\n"
  "Amplitudes of harmonic signals\n"
  "------------------------------\n"
  "Option: -harmonic\n"
  "\n"
  "The Fourier transformation does not exist for harmonic signals. The option\n"
  "\"-harmonic\" supports the analysis of a time limited portion of a harmonic\n"
  "signal. If this option is set, the output is scaled such that the peak values\n"
  "in the spectrum equal the amplitude of the corresponding harmonic time domain\n"
  "signal in units of K.\n"
  "\n"
  "Details of the scaling used for this option are given in doxygen formatted\n"
  "comments at the end of the source code file.\n"
  "\n"
  "The input signal can be extended by padding with zeroes (-pad). This mainly is\n"
  "used to obtain a smoother representation of the corresponding spectral display\n"
  "where the amplitude of narrow peaks might not fall on a spectral node when\n"
  "analysing harmonic signals. The spectral representation consequently is scaled\n"
  "to the length of the applied taper function (and not to the full length of the\n"
  "padded time series) for harmonic signal analysis and power spectral densities,\n"
  "since the signal under investigation is understood as being infinite in time.\n"
  "For amplitude spectra of transient signals (the default) no scaling to a time\n"
  "window takes place, since padding with zeroes is understood as not altering\n"
  "the signal.\n"
};