Chandra X-Ray Observatory
Skip to the navigation links
Last modified: December 2013

Jump to: Description · Examples · Bugs · See Also

AHELP for CIAO 4.10 Sherpa v1


Context: modeling


Freeze model parameters, so they do not vary during a fit.


freeze([parameter], [[parameters]])


Given one or more model parameters, freeze each model parameter at its current value. The frozen parameters are not varied during a fit. (If an argument is a model, then all the model parameters of that model are frozen.)

  • parameter(s) - model parameters to freeze for the fit

One of more model parameters may be specified as a comma-separated list. If the model name is provided without a parameter specified, all of the parameters in the model are frozen.

To unfreeze model parameter values and allow them to vary, the command thaw ("ahelp thaw") is used.


Example 1

sherpa> freeze(g.ampl)

The model parameter "ampl" of model "g" is frozen at its current value.

Example 2

sherpa> freeze(g.ampl, g.fwhm)

Both model parameters "ampl" and "fwhm" of model "g" are frozen at their current values.

Example 3

sherpa> freeze(g)

All model parameters specified in model "g" are frozen at their current values.


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

See Also

guess, link, paramprompt, set_par, thaw, unlink

Last modified: December 2013
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email: Smithsonian Institution, Copyright © 1998-2017. All rights reserved.