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renorm

renormalize model to minimize statistic with current parameters

Renormalize model, or change renorm conditions.

Syntax: renorm [auto|none|prefit]

The renorm command will adjust the normalizations of the model by a single multiplication factor, which is chosen to minimize the fit statistic. Such a renorm will be performed explicitly whenever the command is used without a key-word, or during certain XSPEC commands, as determined by the following key-words:

auto Renormalize after a model or newpar command, and at the beginning of a fit.
prefit Renormalize only at the beginning of a fit.
none Perform no automatic renormalizations, i.e., only perform them when a renorm command is given explicitly.

This command works by doing an analytic calculation to change the normalizations of all additive components in the model to minimize the fit statistic. The relative normalizations of the components will not be changed. This analytic calculation cannot be performed for all the fit statistics, in particular it will not work for cstat if there is a background file. If the analytic calculation is not possible this command will have no effect.


next up previous contents
Next: steppar Up: Fit Commands Previous: margin