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

`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 Index]