FFT

##
FFT

            ANALYSE\FFT [/REMOVE [wmin wmax]]
                        [[s1 e1] [s2 e2] ... [s10 e10] /KILL]
                        [/INDEX] [/OBS] [/NOCURS]

        FFT computes a Fourier transform and plots it. Since Fourier  transforms
        can  not deal with sparse data, blank values in the input data (spectrum
        or index) are replaced by interpolated values.

        The command acts either on a single spectrum (from the R buffer)  or  on
        the  INDEX. The default behavior is defined with SET ACTION, but can al-
        ways be ignored with /OBS or /INDEX.  Identically,  the  option  /NOCURS
        overrides the default cursor.

        Three modes are available (see subtopic for details):
          - no  option:  the  FFT is computed and plotted. The RY values are not
            modified.
          - /KILL allows to linearly interpolate pieces of  the  Fourier  trans-
            form, either interactively or by supplying values.
          - /REMOVE  indicates that the Fourier transform is to be computed from
            a spectrum linearly interpolated in  some  intervals  (specified  or
            taken from the last fitted profiles).

        If  the  action is applied on the R buffer, the result (including /KILL,
        if any) of the FFT is available in the variables R%FFT%X and R%FFT%Y.

        There is no option to customize the FFT plot limits. A custom  plot  can
        be done as follows:
          LAS> FFT  ! Fill the R%FFT%X and R%FFT%Y arrays
          LAS> G\LIMITS /VARIABLES R%FFT%X R%FFT%Y  ! Auto X and Y limits
          LAS> G\LIMITS 0.0 1.0 = =  ! Override X limits with custom values
          LAS> CLEAR
          LAS> G\BOX
          LAS> G\HISTO R%FFT%X R%FFT%Y
          LAS> G\LABEL "Inverse Frequency (MHz\\u-1\d)" /X

Subsections

- FFT /KILL
- FFT /REMOVE