R: Measures of Model Accuracy

accuracy {SDMTools} | R Documentation

## Measures of Model Accuracy

### Description

`accuracy` estimates six measures of accuracy for presence-absence or presence-psuedoabsence data. These include AUC, ommission rates, sensitivity, specificity, proportion correctly identified and Kappa.
Note: this method will exclude any missing data.

### Usage

    accuracy(obs, pred, threshold = 0.5)

### Arguments

`obs` | a vector of observed values which must be 0 for absences and 1 for occurrences
`pred` | a vector of the same length as `obs` representing the predicted values. Values must be between 0 & 1 prepresenting a likelihood.
`threshold` | this can be: a) a single value representing a single threshold between 0 & 1; b) a vector of threshold values between 0 & 1; OR c) an integer value representing the number of equal interval threshold values between 0 & 1

### Value

a data.frame with seven columns:

`threshold` | the threshold values representing each row of data
`AUC` | the AUC given the defined threshold value
`ommission.rate` | the ommission rate as a proportion of true occurrences misidentified given the defined threshold value
`sensitivity` | the sensitivity given the defined threshold value
`specificity` | the specificity given the defined threshold value
`prop.correct` | the proportion of the presence and absence records correctly identified given the defined threshold value
`Kappa` | the Kappa statistic of the model given the defined threshold value

### Author(s)

Jeremy VanDerWal jjvanderwal@gmail.com

### See Also

`auc`, `Kappa`, `omission`, `sensitivity`, `specificity`, `prop.correct`, `confusion.matrix`

### Examples

    #create some data
    obs = c(sample(c(0,1),20,replace=TRUE),NA); obs = obs[order(obs)]
    pred = runif(length(obs),0,1); pred = pred[order(pred)]

    #calculate accuracy of the model with a single threshold value
    accuracy(obs,pred,threshold=0.5)

    #calculate accuracy given several defined thresholds
    accuracy(obs,pred,threshold=c(0.33,0.5,0.66))

    #calculate accuracy given a number of equal interval thresholds
    accuracy(obs,pred,threshold=20)

[Package SDMTools version 1.1-221.2 Index]