Last modified: December 2025

URL: https://cxc.cfa.harvard.edu/sherpa/ahelp/cstatnegativepenalty.html
AHELP for CIAO 4.18 Sherpa

cstatnegativepenalty

Context: statistics

Synopsis

The CStat statistic adjusted to penalize negative model values

Description

The cstatnegativepenalty statistic is the same as the cstat statistic except when the model predicts one or more negative values. In this case the statistic is penalised by the absolute value of the negative value, or values. The aim is to help the optimiser out in moving the fit to a more-physical location in the search space.


Example

sherpa> set_stat("cstatnegativepenalty")
sherpa> get_stat_name()
'cstatnegativepenalty'

Set the fitting statistic and then confirm the new value.


Changes in CIAO 4.18

This statistic is new in CIAO 4.18.


Bugs

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

See Also

info
list_stats
statistics
cash, chi2constvar, chi2datavar, chi2gehrels, chi2modvar, chi2xspecvar, chisquare, cstat, get_prior, leastsq, list_priors, set_prior, set_sampler, set_stat, wstat