# brierScore: Multinominal Brier Score In aqp: Algorithms for Quantitative Pedology

## Description

Compute a multinominal Brier score from predicted class probabilities and observed class label. Lower values are associated with a more accurate classifier.

## Usage

 `1` ```brierScore(x, classLabels, actual = "actual") ```

## Arguments

 `x` `data.frame` of class probabilities (numeric) and observed class label (character), see examples `classLabels` vector of predicted class labels (probabilities), corresponding to column names in `x` `actual` name of column containing the observed class, should be character vector not factor

## Value

a single Brier score, representative of data in `x`

D.E. Beaudette

## References

Brier, Glenn W. 1950. "Verification of Forecasts Expressed in Terms of Probability." Monthly Weather Review 78 (1): 1-3. doi:10.1175/1520-0493(1950)078<0001:VOFEIT>2.0.CO;2.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38``` ```# columns 'a', 'b', 'c' contain predicted probabilities # column 'actual' contains observed class label # a good classifier d.good <- data.frame( a = c(0.05, 0.05, 0.10), b = c(0.90, 0.85, 0.75), c = c(0.05, 0.10, 0.15), actual = c('b', 'b', 'b'), stringsAsFactors = FALSE ) # a rather bad classifier d.bad <- data.frame( a = c(0.05, 0.05, 0.10), b = c(0.90, 0.85, 0.75), c = c(0.05, 0.10, 0.15), actual = c('c', 'c', 'c'), stringsAsFactors = FALSE ) # class labels are factors d.factors <- data.frame( a = c(0.05, 0.05, 0.10), b = c(0.90, 0.85, 0.75), c = c(0.05, 0.10, 0.15), actual = c('b', 'b', 'b'), stringsAsFactors = TRUE ) # relatively low value = accurate brierScore(x = d.good, classLabels = c('a', 'b', 'c'), actual = 'actual') # high values = not accuate brierScore(x = d.bad, classLabels = c('a', 'b', 'c'), actual = 'actual') # message related to conversion of factor -> character brierScore(x = d.factors, classLabels = c('a', 'b', 'c'), actual = 'actual') ```

aqp documentation built on Sept. 29, 2021, 9:09 a.m.