ddalpha.classify {ddalpha} | R Documentation

## Classify using DD-Classifier

### Description

Classifies data using the DD-classifier and a specified outsider treatment.

### Usage

    ddalpha.classify(ddalpha, objects, subset, outsider.method = NULL, use.convex = NULL)

    ## S3 method for class 'ddalpha'
    predict(object, objects, subset, outsider.method = NULL, use.convex = NULL, ...)

### Arguments

`ddalpha, object` | DDα-classifier (obtained by `ddalpha.train`).
`objects` | Matrix containing objects to be classified; each row is one d-dimensional object.
`subset` | an optional vector specifying a subset of observations to be classified.
`outsider.method` | Character string, name of a treatment to be used for outsiders; one of those trained by `ddalpha.train`. If the treatment was specified using the argument `outsider.methods` then use the name of the method.

`use.convex`

Logical variable indicating whether outsiders should be determined as the points not contained in any of the convex hulls of the classes from the training sample (`TRUE`) or those having zero depth w.r.t. each class from the training sample (`FALSE`). For `depth =` `"zonoid"` both values give the same result. If `NULL` the value specified in DDα-classifier (in `ddalpha.train`) is used.

`...` | additional parameters are ignored

### Details

Only one outsider treatment can be specified.

See Lange, Mosler and Mozharovskyi (2014) for details and additional information.

### Value

List containing class labels, or character string "Ignored" for the outsiders if "Ignore" was specified as the outsider treating method.

### References

Dyckerhoff, R., Koshevoy, G., and Mosler, K. (1996). Zonoid data depth: theory and computation. In: Prat A. (ed), COMPSTAT 1996. Proceedings in computational statistics, Physica-Verlag (Heidelberg), 235–240.

Lange, T., Mosler, K., and Mozharovskyi, P. (2014). Fast nonparametric classification based on data depth. Statistical Papers 55 49–69.

Li, J., Cuesta-Albertos, J.A., and Liu, R.Y. (2012). DD-classifier: Nonparametric classification procedure based on DD-plot. Journal of the American Statistical Association 107 737–753.

Mozharovskyi, P. (2015). Contributions to Depth-based Classification and Computation of the Tukey Depth. Verlag Dr. Kovac (Hamburg).

Mozharovskyi, P., Mosler, K., and Lange, T. (2015). Classifying real-world data with the DDα-procedure. Advances in Data Analysis and Classification 9 287–314.

Vasil'ev, V.I. (2003). The reduction principle in problems of revealing regularities I. Cybernetics and Systems Analysis 39 686–694.

### See Also

`ddalpha.train` to train the DD-classifier.

### Examples

    # Generate a bivariate normal location-shift classification task
    # containing 200 training objects and 200 to test with
    class1 <- mvrnorm(200, c(0,0),
                      matrix(c(1,1,1,4), nrow = 2, ncol = 2, byrow = TRUE))
    class2 <- mvrnorm(200, c(2,2),
                      matrix(c(1,1,1,4), nrow = 2, ncol = 2, byrow = TRUE))
    trainIndices <- c(1:100)
    testIndices <- c(101:200)
    propertyVars <- c(1:2)
    classVar <- 3
    trainData <- rbind(cbind(class1[trainIndices,], rep(1, 100)),
                       cbind(class2[trainIndices,], rep(2, 100)))
    testData <- rbind(cbind(class1[testIndices,], rep(1, 100)),
                      cbind(class2[testIndices,], rep(2, 100)))
    data <- list(train = trainData, test = testData)

    # Train the DDalpha-Classifier (zonoid depth, maximum Mahalanobis depth
    # classifier with defaults as outsider treatment)
    ddalpha <- ddalpha.train(data$train,
                             depth = "zonoid",
                             outsider.methods = "depth.Mahalanobis")
    # Get the classification error rate
    classes <- ddalpha.classify(data$test[,propertyVars], ddalpha,
                                outsider.method = "depth.Mahalanobis")
    cat("Classification error rate: ",
        sum(unlist(classes) != data$test[,classVar])/200, ".\n", sep="")

[Package ddalpha version 1.3.1 Index]