Allow model parameters to be varied during a fit.

The arguments can be parameters or models, in which case all parameters of the model are thawed. If no arguments are given then nothing is changed.


args (sequence of str or Parameter or Model) – The parameters or models to thaw.

See also


Fit one or more data sets.


Fix model parameters so they are not changed by a fit.


Link a parameter value to an associated value.


Set the value, limits, or behavior of a model parameter.


Unlink a parameter value.


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

Certain parameters may be marked as “always frozen”, in which case using the parameter in a call to thaw will raise an error. If the model is sent to thaw then the “always frozen” parameter will be skipped.


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()

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

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

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

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