Implements the signal model discussed in `spectralem()`. Doesn't include any \(f_i\).
Parameters are passed in a list params with components amp
, pos
, gwidth
and lwidth
which are vectors of the same length.
For each the i-th entry yields the parameters of the i-th Voigt profile.
Furthermore named components a
and b
describe the slope and offset of the linear background respectively. See examples.