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resemble (version 2.1.2)

opls_for_projection: orthogonal scores algorithn of partial leat squares (opls) projection

Description

Computes orthogonal socres partial least squares (opls) projection with the NIPALS algorithm. It allows multiple response variables. Although the main use of the function is for projection, it also retrieves regression coefficients. NOTE: For internal use only!

Usage

opls_for_projection(X, Y, ncomp, scale,
                    maxiter, tol,
                    pcSelmethod = "var",
                    pcSelvalue = 0.01, 
                    algorithm = "pls", 
                    xls_min_w = 3, 
                    xls_max_w = 15)

Value

a list containing the following elements:

  • coefficients the matrix of regression coefficients.

  • bo a matrix of one row containing the intercepts for each component.

  • scores the matrix of scores.

  • X_loadings the matrix of X loadings.

  • Y_loadings the matrix of Y loadings.

  • projection_mat the projection matrix.

  • Y the Y input.

  • variance a list conating two objects: x_var and y_var. These objects contain information on the explained variance for the X and Y matrices respectively.

  • transf a list conating two objects: Xcenter and Xscale.

  • weights the matrix of wheights.

Arguments

X

a matrix of predictor variables.

Y

a matrix of either a single or multiple response variables.

ncomp

the number of pls components.

scale

logical indicating whether X must be scaled.

maxiter

maximum number of iterations.

tol

limit for convergence of the algorithm in the nipals algorithm.

pcSelmethod

if regression = TRUE, the method for selecting the number of components. Options are: 'manual', 'cumvar' (for selecting the number of principal components based on a given cumulative amount of explained variance) and 'var' (for selecting the number of principal components based on a given amount of explained variance). Default is 'cumvar'.

pcSelvalue

a numerical value that complements the selected method (pcSelmethod). If 'cumvar' is chosen (default), pcSelvalue must be a value (larger than 0 and below 1) indicating the maximum amount of cumulative variance that the retained components should explain. Default is 0.99. If 'var' is chosen, pcSelvalue must be a value (larger than 0 and below 1) indicating that components that explain (individually) a variance lower than this threshold must be excluded. If 'manual' is chosen, pcSelvalue has no effect and the number of components retrieved are the one specified in ncomp.

algorithm

(for weights computation) a character string indicating what method to use. Options are: 'pls' for pls (using covariance between X and Y), 'mpls' for modified pls (using correlation between X and Y) or 'xls' for extended pls (as implemented in BUCHI NIRWise PLUS software).

xls_min_w

(for weights computation) an integer indicating the minimum window size for the "xls" method. Only used if algorithm = 'xls'. Default is 3 (as in BUCHI NIRWise PLUS software).

xls_max_w

(for weights computation) an integer indicating the maximum window size for the "xls" method. Only used if algorithm = 'xls'. Default is 15 (as in BUCHI NIRWise PLUS software).

Author

Leonardo Ramirez-Lopez