preProcess {caret}R Documentation

Pre-Processing of Predictors

Description

Pre-processing transformation (centering, scaling etc) can be estimated from the training data and applied to any data set with the same variables.

Usage

preProcess(x, ...)

## Default S3 method:
preProcess(x, method = c("center", "scale"), 
           thresh = 0.95, na.remove = TRUE, ...)

## S3 method for class 'preProcess':
predict(object, newdata, ...)

Arguments

x a matrix or data frame
method a character vector specifying the type of processing. Possible values are "center", "scale", "pca" and "spartialSign"
thresh a cutoff for the cumulative percent of variance to be retained by PCA
na.remove a logical; should missing values be removed from the calculations?
object an object of class preProcess
newdata a matrix or data frame of new data to be pre-processed
... Additional arguments (currently this argument is not used)

Details

The operations are applied in this order: centering, scaling, PCA and spatial sign. If PCA is requested but scaling is not, the values will still be scaled.

The function will throw an error of any variables in x has less than two unique values.

Value

preProcess results in a list with elements

call the function call
dim the dimensions of x
mean a vector of means (if centering was requested)
std a vector of standard deviations (if scaling or PCA was requested)
rotation a matrix of eigenvectors if PCA was requested
method the value ofmethod
thresh the value ofthresh
numComp the number of principal components required of capture the specified amount of variance

Author(s)

Max Kuhn

References

Kuhn (2008), ``Building Predictive Models in R Using the caret'' (http://www.jstatsoft.org/v28/i05/)

See Also

prcomp, spatialSign

Examples

data(BloodBrain)
# one variable has one unique value
## Not run: preProc <- preProcess(bbbDescr[1:100,])

preProc <- preProcess(bbbDescr[1:100,-3])
training <- predict(preProc, bbbDescr[1:100,-3])
test <- predict(preProc, bbbDescr[101:208,-3])

[Package caret version 4.10 Index]