Note

You are not reading the most up to date version of Gammapy documentation.
Access the latest stable version v1.3 or the list of Gammapy releases.

cash

gammapy.stats.cash(n_on, mu_on)

Cash statistic, for Poisson data.

The Cash statistic is defined as:

$$C = 2 \left( \mu_{on} - n_{on} \log \mu_{on} \right)$$

and $C = 0$ where $\mu <= 0$. For more information see Fit statistics

Parameters

n_onarray_like

Observed counts

mu_onarray_like

Expected counts

Returns

statndarray

Statistic per bin

References

• Sherpa statistics page section on the Cash statistic

• Sherpa help page on the Cash statistic

• Cash 1979, ApJ 228, 939