# ARTS built-in documentation server

## Workspace Method jacobianAddSinefit

### Description

Includes sinusoidal baseline fit in the Jacobian.
Works as jacobianAddPolyfit, beside that a series of sine and
cosine terms are used for the baseline fit.
For each value in ``period_lengths`` one sine and one cosine term are
included (in mentioned order). By these two terms the amplitude and
"phase" for each period length can be determined. The sine and
cosine terms have value 0 and 1, respectively, for first frequency.
If the simulation/retrieval deals with a single spectrum, the number
of elements added to the state vector (x) is 2 * nperiods, where
nperiods is the length of ``period_lengths``. The same is true
if ``no_pol_variation``, ``no_los_variation`` and ``no_mblock_variation``
all are set to 1, even if several spectra are involved. Otherwise thenumber of elements added to x depends on the number of spectra and
the settings of ``no_pol_variation``, ``no_los_variation`` and
``no_mblock_variation``. The sine and cosine terms for each period
length are treated as a separate retrieval quantities. That is, the
the elements associated with the first period length are grouped and
form together a retrieval quantity, etc. Inside each retrieval quantity
the pairs of sine and cosine terms are kept together, in given order.

**Authors: **Patrick Eriksson

### Synopsis

### Variables