Last modified: December 2020

URL: https://cxc.cfa.harvard.edu/sherpa/ahelp/thaw.html
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AHELP for CIAO 4.13 Sherpa v1

thaw

Context: modeling

Synopsis

Allow model parameters to be varied during a fit.

Syntax

thaw(*args)

Description

If called with no arguments, then all parameters of models in source expressions are thawed. The arguments can be parameters or models (in which case all parameters of the model are thawed).


Examples

Example 1

Ensure that the FWHM parameter of the line model (in this case a `gauss1d` model) will be varied in any fit.

>>> set_source(const1d.bgnd + gauss1d.line)
>>> thaw(line.fwhm)
>>> fit()

Example 2

Thaw all parameters of the line model and then re-fit:

>>> thaw(line)
>>> fit()

Example 3

Thaw the nh parameter of the gal model and the abund parameter of the src model:

>>> thaw(gal.nh, src.abund)

Notes

The `freeze` function can be used to reverse this setting, so that parameters are "frozen" and so remain constant during a fit.


Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

contrib
renorm
fitting
fit
modeling
freeze, guess, link, paramprompt, set_par, unlink