count2prob: Convert Ensemble Counts to Probabilities

View source: R/count2prob.R

count2probR Documentation

Convert Ensemble Counts to Probabilities


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).


count2prob(x, type = 3)



input matrix of counts from convert2prob


selection of plotting positions (default to 3, see Types)


Matrix of probabilities per category


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

p(x_i) = \frac{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


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


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, ]

easyVerification documentation built on Aug. 15, 2023, 9:06 a.m.