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SMODEL
Creates or updates a fit_model data object containing a composite
model (cmodel) specification and initial values and ranges for
the parameter set associated with each component primitive model
(pmodel). Pmodels all have keywords consisting of two
alphanumeric characters and may be of two basic types. Additive
pmodels (e.g. BR, = bremmstrahlung) have units of flux, whilst
multiplicative models (e.g. AB, =absorption) are dimensionless,
and act to modify the additive model components. Cmodels are
specified using a straightforward mathematical syntax in which
brackets and + - and * operations are allowed, for example:
PL + AB * (BR - LG)
The cmodel is checked by the program, and translated into a
reverse Polish string from which it is more readily computed.
If an existing fit_model object with the required name is found
then its model prescription will be displayed, and you will be
asked if you want to accept it or overwrite it with a new
prescription.
Finally the default or existing parameter values for each model
component, as well as their lower and upper bounds, will be
displayed. You may accept these values, or define new ones (one,
two or three numbers can be entered). The bounds are used by
fitting routines to prevent unphysical or uninteresting regions
of parameter space being accessed.
Subtopics:
Next: Input Output Data Up: Spectral Fitting commands Prev: SMHELP