R: Class "performance"

performance-class {ROCR} | R Documentation

## Class "performance"

### Description

Object to capture the result of a performance evaluation, optionally collecting evaluations from several cross-validation or bootstrapping runs.

### Details

A `performance` object can capture information from four different evaluation scenarios:

- The behaviour of a cutoff-dependent performance measure across the range of all cutoffs (e.g. `performance( predObj, 'acc' )` ). Here, `x.values` contains the cutoffs, `y.values` the corresponding values of the performance measure, and `alpha.values` is empty.

- The trade-off between two performance measures across the range of all cutoffs (e.g. `performance( predObj, 'tpr', 'fpr' )` ). In this case, the cutoffs are stored in `alpha.values`, while `x.values` and `y.values` contain the corresponding values of the two performance measures.

- A performance measure that comes along with an obligatory second axis (e.g. `performance( predObj, 'ecost' )` ). Here, the measure values are stored in `y.values`, while the corresponding values of the obligatory axis are stored in `x.values`, and `alpha.values` is empty.

- A performance measure whose value is just a scalar (e.g. `performance( predObj, 'auc' )` ). The value is then stored in `y.values`, while `x.values` and `alpha.values` are empty.

### Objects from the Class

Objects can be created by using the `performance` function.

### Slots

`x.name`:

  Performance measure used for the x axis.

`y.name`:

  Performance measure used for the y axis.

`alpha.name`:

  Name of the unit that is used to create the parametrized curve. Currently, curves can only be parametrized by cutoff, so `alpha.name` is either `none` or `cutoff`.

`x.values`:

  A list in which each entry contains the x values of the curve of this particular cross-validation run. x.values[[i]], y.values[[i]], and alpha.values[[i]] correspond to each other.

`y.values`:

  A list in which each entry contains the y values of the curve of this particular cross-validation run.

`alpha.values`:

  A list in which each entry contains the cutoff values of the curve of this particular cross-validation run.

### Author(s)

Tobias Sing tobias.sing@mpi-sb.mpg.de, Oliver Sander osander@mpi-sb.mpg.de

### References

A detailed list of references can be found on the ROCR homepage at http://rocr.bioinf.mpi-sb.mpg.de.

### See Also

`prediction`, `performance`, `prediction-class`, `plot.performance`

[Package ROCR version 1.0-7 Index]