afc.np {afc} | R Documentation |

## 2AFC For Nominal Polychotomous Observations Ans Probabilistic Forecasts

### Description

Routine to calculate the Generalized Discrimination Score (aka Two-Alternatives Forced Choice Score 2AFC) for the situation of polychotomous (nominal) observations and discrete probabilistic forecasts

### Usage

```
afc.np(obsv, fcst, m = 3)
```

### Arguments

`obsv` |
vector with dichotomous observations (values in 0,1) |

`fcst` |
two-dimensional array with forecast probabilities for the m categories; dim(fcst)[1] = length(obsv); dim(fcst)[2] = m |

`m` |
number of observation categories (default = 3) |

### Details

This routine applies Eq.17 of Mason and Weigel (2009) to calculate the 2AFC.

### Value

`p.afc` |
Value of Generalized Discrimination (2AFC) Score |

### Author(s)

Andreas Weigel, Federal Office of Meteorology and Climatology, MeteoSwiss, Zurich, Switzerland

### References

S.J. Mason and A.P. Weigel, 2009. A generic verification framework for administrative purposes. Mon. Wea. Rev., 137, 331-349

### See Also

### Examples

```
#Forecasts and observations of Nino-3.4 index
#Load set of polychotomous observations (4 categories) and probabilistic forecasts
data(cnrm.nino34.mp)
obsv = cnrm.nino34.mp$obsv
fcst = cnrm.nino34.mp$fcst
#Calculate skill score
afc.np(obsv,fcst,4)
```

*afc*version 1.4.0 Index]