Calculation of amplitude/phase variations
If you suspect that the amplitude and/or phase of a parameter is variable
within different substrings (e.g. representing different years) you might consider to use this tool.
- Prerequisites:
Let us assume that you have a set of frequencies and a certain subdivision of
your time string in the attribute "Date". By calculating a least-squares
fit for each substring separately you realized that the amplitude of
a frequency might be variable.
- Press the button "Calculate amplitude/phase variations" in the Fit module.
- In the dialog select the attribute in which the subdivision of the
time string is located.
- Choose the type of variation: 'amplitude variation', 'phase
variation' or 'amplitude and phase variations'.
- Select the frequency that shows the amplitude variation.
- Decide whether you want to improve "all amplitudes and phases" while keeping
the frequencies fixed, or to define a "special" selection of variable
parameters. If you prefer the latter, then click on special to open a dialog
for the definition of the selection.
- Press Calculate to start the calculation.
- After the calculation has finished the results are displayed in the text
box below.