rps {verification} | R Documentation

## Ranked Probability Score

### Description

Calculates the ranked probability score (rps) and ranked probability skill score (rpss) for probabilistic forecasts of ordered events.

### Usage

     rps(obs, pred, baseline=NULL)

### Arguments

`obs` | A vector of observed outcomes. These values correspond to columns of prediction probabilities.
`pred` | A matrix of probabilities for each outcome occurring. Each column represents a category of prediction.
`baseline` | If NULL (default) the probability based on the sample data of each event to occur. Alternatively, a vector the same length of the as the number categories can be entered.

### Value

`rps` | Ranked probability scores
`rpss` | Ranked probability skill score. Uses baseline or sample climatology as a references score.
`rps.clim` | Ranked probability score for baseline forecast.

### Note

Perhaps the format of the data is best understood in the context of an example. Consider a probability of precipitation forecast of "none", "light" or "heavy". This could be [0.5, 0.3, 0.2]. If heavy rain occurred, the observed value would be 3, indicating event summarized in the third column occurred.

The RPS value is scaled to a [0,1 ] interval by dividing by (number of categories -1 . There is a discrepancy in the way this is explained in Wilks (2005) and the WWRF web page.

### Author(s)

Matt Pocernich <pocernic@rap.ucar.edu>

### References

WWRP/WGNE Joint Working Group on Verification - Forecast Verification - Issues, Methods and FAQ http://www.bom.gov.au/bmrc/wefor/staff/eee/verif/verif_web_page.html#RPS

Wilks, D. S. (2005) Statistical Methods in the Atmospheric Sciences Chapter 7, San Diego: Academic Press.

### See Also

`crps`

### Examples

    ###  Example from Wilks, note without a baseline and only one
    ### forecast, the rpss and ss are not too meaningfull.

    rps( obs = c(1), pred = matrix(c(0.2, 0.5, 0.3), nrow = 1))

[Package verification version 1.20 Index]