Chi2XspecVar
- class sherpa.stats.Chi2XspecVar(name='chi2xspecvar')[source] [edit on github]
Bases:
Chi2
Chi Squared with data variance (XSPEC style).
The variance in each bin is estimated from the data value in that bin.
The calculation of the variance is the same as
Chi2DataVar
except that if the number of counts in a bin is less than 1 then the variance for that bin is set to 1.See also
Methods Summary
calc_chisqr
(data, model)Return the chi-square value for each bin.
calc_stat
(data, model)Return the statistic value for the data and model.
calc_staterror
(data)Return the statistic error values for the data.
goodness_of_fit
(statval, dof)Return the reduced statistic and q value.
Methods Documentation
- calc_chisqr(data, model) [edit on github]
Return the chi-square value for each bin.
- Parameters
data (
sherpa.data.Data
orsherpa.data.DataSimulFit
) – The data set, or sets, to use.model (
sherpa.models.model.Model
orsherpa.models.model.SimulFitModel
) – The model expression, or expressions. If asherpa.models.model.SimulFitModel
is given then it must match the number of data sets in the data parameter.
- Returns
chisqr – The per-bin chi-square values.
- Return type
array of numbers
- calc_stat(data, model) [edit on github]
Return the statistic value for the data and model.
- Parameters
data (
sherpa.data.Data
orsherpa.data.DataSimulFit
) – The data set, or sets, to use.model (
sherpa.models.model.Model
orsherpa.models.model.SimulFitModel
) – The model expression, or expressions. If asherpa.models.model.SimulFitModel
is given then it must match the number of data sets in the data parameter.
- Returns
statval (number) – The value of the statistic.
fvec (array of numbers) – The per-bin “statistic” value.
- static calc_staterror(data)[source] [edit on github]
Return the statistic error values for the data.
- Parameters
data (scalar or 1D array of numbers) – The data values.
- Returns
staterror – The errors for the input data values (matches the data argument).
- Return type
scalar or array of numbers
- goodness_of_fit(statval, dof) [edit on github]
Return the reduced statistic and q value.
The reduced statisitc is conceptually simple, as it is just statistic / degrees-of-freedom, but it is not meaningful for all statistics, and it is only valid if there are any degrees of freedom.
- Parameters
- Returns
rstat (float or NaN or None) – The reduced statistic. If the statistic does not support a goodness of fit then the return value is
None
. If it does then NaN is returned if either the number of degrees of freedom is 0 (or less), or the statistic value is less than 0.qval (float or NaN or None) – The q value. If the statistic does not support a goodness of fit then the return values are
None
. If it does then NaN is returned if either the number of degrees of freedom is 0 (or less), or the statistic value is less than 0.