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cstat

gammapy.stats.cstat(n_on, mu_on, n_on_min=1e-25)[source]

C statistic, for Poisson data.

The C statistic is defined as

C=2[μon−non+non(log(non)−log(μon)]

and C=0 where μon<=0.

n_on_min handles the case where n_on is 0 or less and the log cannot be taken. For more information see Fit statistics

Parameters
n_onarray_like

Observed counts

mu_onarray_like

Expected counts

n_on_minarray_like

n_on = n_on_min where n_on <= n_on_min.

Returns
statndarray

Statistic per bin

References