get_covar

get_covar();
get_covar_results();
get_covar_opt( [name] );

Description

get_covar

The get_covar command returns the current covariance estimation method object. The function accepts no arguments. The returned information includes:

• sigma - to get 1, 2, or 3-sigma limits
• eps - precision of resulting limits
• maxiters- maximum number of tries to bracket desired limits, before returning
• soft_limits - a switch which allows the search to go all the way out to the hard parameter limits; if switched on, the search will be restricted to occur within the soft limits, which can be changed by the user

get_covar_results

The get_covar_results command accesses results from the last time covariance was run. The function accepts no arguments. The results include the following attributes:

• datasets - Data sets in fit
• methodname - Estimation method name
• fitname - Fitting method name
• statname - Statistic name
• percent
• sigma - Change in statistic
• parnames - Model parameter names
• parvals - Model parameter fit values
• parmins - Model parameter minimum values
• parmaxes - Model parameter maximum values
• extra_output - the covariance matrix

get_covar_opt

The get_covar_opt command returns a covariance option by name. If the name isn't specified, it returns a dictionary of all options that govern how covariance is run.

• sigma - to get 1, 2, or 3-sigma limits, default=0.01
• eps - precision of resulting limits, default=0.01
• maxiters- maximum number of tries to bracket desired limits, before returning, default=200
• soft_limits - a switch which allows the search to go all the way out to the hard parameter limits; if switched on, the search will be restricted to occur within the soft limits, which can be changed by the user, default=False

sherpa> get_covar();

sherpa> print(get_covar());
name        = covariance
soft_limits = False
maxiters    = 200
sigma       = 1
eps         = 0.01

sherpa> get_covar_results();

sherpa> print(get_covar_results());
data sets   = (2,)
methodname = covariance
fitname    = levmar
statname   = chi2gehrels
sigma      = 1
percent    = 68.2689492137
parnames   = ('p2.gamma', 'p2.ampl')
parvals    = (1.0, 1.0)
parmins    = (-2.5123712497785912e-05, -1.8031410361942839e-05)
parmaxes   = (2.5123712497785912e-05, 1.8031410361942839e-05)
nfits      = 0

sherpa> get_covar_opt("sigma");
1