nnetEval {chemometrics} | R Documentation

## Neural network evaluation by CV

### Description

Evaluation for Artificial Neural Network (ANN) classification by cross-validation

### Usage

    nnetEval(X, grp, train, kfold = 10, decay = seq(0, 10, by = 1), size = 30, maxit = 100,
    plotit = TRUE, legend = TRUE, legpos = "bottomright", ...)

### Arguments

`X` | standardized complete X data matrix (training and test data)
`grp` | factor with groups for complete data (training and test data)
`train` | row indices of X indicating training data objects
`kfold` | number of folds for cross-validation
`decay` | weight decay, see `nnet`, can be a vector with several values - but then "size" can be only one value
`size` | number of hidden units, see `nnet`, can be a vector with several values - but then "decay" can be only one value
`maxit` | maximal number of iterations for ANN, see `nnet`
`plotit` | if TRUE a plot will be generated
`legend` | if TRUE a legend will be added to the plot
`legpos` | positioning of the legend in the plot
`...` | additional plot arguments

### Details

The data are split into a calibration and a test data set (provided by "train"). Within the calibration set "kfold"-fold CV is performed by applying the classification method to "kfold"-1 parts and evaluation for the last part. The misclassification error is then computed for the training data, for the CV test data (CV error) and for the test data.

### Value

`trainerr` | training error rate
`testerr` | test error rate
`cvMean` | mean of CV errors
`cvSe` | standard error of CV errors
`cverr` | all errors from CV
`decay` | value(s) for weight decay, taken from input
`size` | value(s) for number of hidden units, taken from input

### Author(s)

Peter Filzmoser <P.Filzmoser@tuwien.ac.at>

### References

K. Varmuza and P. Filzmoser: Introduction to Multivariate Statistical Analysis in Chemometrics. CRC Press, Boca Raton, FL, 2009.

### See Also

`nnet`

### Examples

    data(fgl,package="MASS")
    grp=fgl$type
    X=scale(fgl[,1:9])
    k=length(unique(grp))
    dat=data.frame(grp,X)
    n=nrow(X)
    ntrain=round(n*2/3)
    require(nnet)
    set.seed(123)
    train=sample(1:n,ntrain)
    resnnet=nnetEval(X,grp,train,decay=c(0,0.01,0.1,0.15,0.2,0.3,0.5,1),
       size=20,maxit=20)

[Package chemometrics version 0.6 Index]