R: Convert Ensemble Counts to Probabilities

count2prob {easyVerification} | R Documentation

## Convert Ensemble Counts to Probabilities

### Description

Using plotting positions as described in Wilks (2011), counts of occurrences per forecast category are converted to probabilities of occurrence. For ensembles of size 1 (e.g. verifying observations), the count vector is returned unaltered (corresponding to occurrence probabilities of 0 or 1).

### Usage

    count2prob(x, type = 3)

### Arguments

`x` | input matrix of counts from `convert2prob`
`type` | selection of plotting positions (default to 3, see Types)

### Value

Matrix of probabilities per category

### Types

The types characterize the plotting positions as specified in Wilks (2011). The plotting positions are computed using the following relationship:

p(x_i) = (i + 1 - a)/(n + 1 - a)

where i is the number of ensemble members not exceeding x, and n is the number of ensemble members. The types are characterized as follows:

type | description | a
1 | Weibull | 0
2 | Bernard and Bos-Levenbach | 0.3
3 | Tukey | 1/3
4 | Gumbel | 1
5 | Hazen | 1/2
6 | Cunnane | 2/5

### References

Wilks, D.S. (2011). Statistical methods in the atmospheric sciences (Third Edition). Academic press.

### See Also

`convert2prob` for conversion of continuous forecasts to ensemble counts

### Examples

    tm <- toymodel()

    ## convert to tercile forecasts (only display first forecast and obs)
    count2prob(convert2prob(tm$fcst, prob=1:2/3))[1,]
    count2prob(convert2prob(tm$obs, prob=1:2/3))[1,]

[Package easyVerification version 0.4.4 Index]