plsdof (version 0.2-1)

benchmark.pls: Comparison of model selection criteria for Partial Least Squares Regression.

Description

This function computes the test error over several runs for different model selection strategies.

Usage

benchmark.pls(X,y,m,R,ratio,verbose,k,ratio.samples,use.kernel,criterion,true.coefficients)

Arguments

X

matrix of predictor observations.

y

vector of response observations. The length of y is the same as the number of rows of X.

m

maximal number of Partial Least Squares components. Default is m=ncol(X).

R

number of runs. Default is 20.

ratio

ratio no of training examples/(no of training examples + no of test examples). Default is 0.8

verbose

If TRUE, the functions plots the progress of the function. Default is TRUE.

k

number of cross-validation splits. Default is 10.

ratio.samples

Ratio of (no of training examples + no of test examples)/nrow(X). Default is 1.

use.kernel

Use kernel representation? Default is use.kernel=FALSE.

criterion

Choice of the model selection criterion. One of the three options aic, bic, gmdl. Default is "bic".

true.coefficients

The vector of true regression coefficients (without intercept), if available. Default is NULL.

Value

• MSE
  data frame of size R x 5. It contains the test error for the five different methods over the R runs.
• M
  data frame of size R x 5. It contains the optimal number of components for the five different methods over the R runs.
• DoF
  data frame of size R x 5. It contains the optimal Degrees of Freedom for the five different methods over the R runs.
• TIME
  data frame of size R x 4. It contains the run for all methods (apart from the zero model) over the R runs.
• M.CRASH
  data frame of size R x 2. It contains the number of components for which the Krylov representation and the Lanczos representation return negative Degrees of Freedom, hereby indicating numerical problems.
• ME
  if true.coefficients are available, this is a data frame of size R x 5. It contains the model error for the five different methods over the R runs.
• SIGMAHAT
  data frame of size R x 5. It contains the estimation of the noise level provided by the five different methods over the R runs.

Details

The function estimates the optimal number of PLS components based on four different criteria: (1) Cross-validation, (2) information criteria with the naive Degrees of Freedom DoF(m)=M+1, (3) information criteri with the Degrees of Freedom computed via a Lanczos represenation of PLS and (4) information criteri with the Degrees of Freedom computed via a Krylov represenation of PLS. Note that the latter two options only differ with respect to the estimation of the model error. In addition, the function computes the test error of the "zero model", i.e. mean(y) on the training data is used for prediction. If true.coefficients are available, the function also computes the model error for the different methods, i.e. the sum of squared differences between the true and the estimated regression coefficients.

References

Kraemer, N., Sugiyama M. (2010). "The Degrees of Freedom of Partial Least Squares Regression". preprint, http://arxiv.org/abs/1002.4112

See Also

pls.ic, pls.cv

Examples

# to do