Chandra X-Ray Observatory
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Last modified: December 2010

URL: http://cxc.harvard.edu/sherpa/freeze.html
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AHELP for CIAO 4.3 Sherpa v1

freeze

Context: modeling

Synopsis

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

Syntax

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

Description

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

The freeze function must be given at least one argument. That argument must be a model or a model parameter. The function can be given an indefinite number of models and/or model parameters as arguments. If a model is an argument, all the parameters of that model are frozen at their current values.

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.

Bugs

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

See Also

modeling
guess, link, paramprompt, set_par, thaw, unlink

Last modified: December 2010
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