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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
Gildas manager
2024-04-19