R: Interface to SVMlight

svmlight {klaR} | R Documentation

## Interface to SVMlight

### Description

Function to call SVMlight from R for classification. Multiple group classification is done with the one-against-rest partition of data.

### Usage

    svmlight(x, ...)

    ## Default S3 method:
    svmlight(x, grouping, temp.dir = NULL, pathsvm = NULL,
        del = TRUE, type = "C", class.type = "oaa", svm.options = NULL,
        prior = NULL, out = FALSE, ...)
    ## S3 method for class 'data.frame'
    svmlight(x, ...)
    ## S3 method for class 'matrix'
    svmlight(x, grouping, ..., subset, na.action = na.fail)
    ## S3 method for class 'formula'
    svmlight(formula, data = NULL, ..., subset,
        na.action = na.fail)

### Arguments

`x` | matrix or data frame containing the explanatory variables (required, if `formula` is not given).
`grouping` | factor specifying the class for each observation (required, if `formula` is not given).
`formula` | formula of the form `groups ~ x1 + x2 + ...`. That is, the response is the grouping factor and the right hand side specifies the (non-factor) discriminators.
`data` | Data frame from which variables specified in `formula` are preferentially to be taken.
`temp.dir` | directory for temporary files.
`pathsvm` | Path to SVMlight binaries (required, if path is unknown by the OS).
`del` | Logical: whether to delete temporary files
`type` | Perform `"C"`=Classification or `"R"`=Regression
`class.type` | Multiclass scheme to use. See details.
`svm.options` | Optional parameters to SVMlight. For further details see: “How to use” on http://svmlight.joachims.org/.
`prior` | A Priori probabilities of classes.
`out` | Logical: whether SVMlight output ahouild be printed on console (only for Windows OS.)
`subset` | An index vector specifying the cases to be used in the training sample. (Note: If given, this argument must be named.)
`na.action` | specify the action to be taken if `NA`s are found. The default action is for the procedure to fail. An alternative is `na.omit`, which leads to rejection of cases with missing values on any required variable. (Note: If given, this argument must be named.)
`...` | currently unused

### Details

Function to call SVMlight from R for classification (`type="C"`). SVMlight is an implementation of Vapnik's Support Vector Machine. It is written in C by Thorsten Joachims. On the homepage (see below) the source-code and several binaries for SVMlight are available. If more then two classes are given the SVM is learned by the one-against-all scheme (`class.type="oaa"`). That means that each class is trained against the other K-1 classes. The class with the highest decision function in the SVM wins. So K SVMs have to be learned. If `class.type="oao"` each class is tested against every other and the final class is elected by a majority vote.

If `type="R"` a SVM Regression is performed.

### Value

A list containing the function call and the result of SVMlight.

### Requirements

SVMlight (http://svmlight.joachims.org/) must be installed before using this interface.

### Author(s)

Karsten Luebke, karsten.luebke@fom.de, Andrea Preusser

### References

http://svmlight.joachims.org/

### See Also

`predict.svmlight`,`svm`,

### Examples

    ## Not run:
    ## Only works if the svmlight binaries are in the path.
    data(iris)
    x <- svmlight(Species ~ ., data = iris)
    ## Using RBF-Kernel with gamma=0.1:
    data(B3)
    x <- svmlight(PHASEN ~ ., data = B3, svm.options = "-t 2 -g 0.1")

    ## End(Not run)

[Package klaR version 0.6-12 Index]