# Simpls

Revision as of 14:14, 23 September 2016 by imported>Benjamin

## Contents

### Purpose

Partial Least Squares regression using the SIMPLS algorithm.

### Synopsis

- [reg,ssq,xlds,ylds,wts,xscrs,yscrs,basis] = simpls(x,y,
*ncomp,options*)

### Description

SIMPLS performs PLS regression using SIMPLS algorithm.

#### Inputs

**x**= X-block (predictor block) class "double" or "dataset", and**y**= Y-block (predicted block) class "double" or "dataset".

#### Optional Inputs

= integer, number of latent variables to use in {default = rank of X-block}, and**ncomp****options**= a structure array discussed below.

#### Outputs

**reg**= matrix of regression vectors where each row corresponds to a regression vector for a given number of latent variables. If the Y-block contains multiple columns, the rows of**reg**will be in groups of latent variables (so that the regression vectors for all columns of Y at 1 latent variable will come first, followed by the regression vectors for all columns of Y at 2 latent variables, etc)

- where b
_{yn,k}is the regression vector for column "n" of the Y-block calculated from "k" latent variables.

**ssq**= the sum of squares captured (ssq) with the columns:

- Column 1 = Number of latent variables (LVs)
- Column 2 = Variance captured (as a percent) in the X-block by this LV
- Column 3 = Total variance captured (%) by all LVs up to this row
- Column 4 = Variance captured (as a percent) in the X-block by this LV
- Column 5 = Total variance captured (%) by all LVs up to this row

**xlds**= X-block loadings (size: x-block columns by LVs),**ylds**= Y-block loadings (size: y-block columns by LVs),**wts**= X-block weights (size: x-block columns by LVs),**xscrs**= X-block scores (size: samples by LVs),**yscrs**= Y-block scores (size: samples by LVs),**basis**= the basis of X-block loadings (size: x-block columns by LVs).

**NOTE:** in previous versions of SIMPLS, the X-block scores were unit length and the X-block loadings contained the variance. As of Version 3.0, this algorithm now uses standard convention in which the X-block scores contain the variance.

The calculations for Variance Captured is shown here:

- Xlds = ((X*wts)’X)’
- Ylds = Y’YX*wts
- ssqX = ΣΣ(X.^2)
- ssqY = ΣΣ(Y.^2)

- VarX = diag(Xlds’*Xlds)/ssqX
- VarY = diag(Ylds’*Ylds)/ssqY

### Options

*options* = a structure array with the following fields:

**display**: [ {'on'} | 'off' ], governs level of display, and**ranktest**: [ 'none' | 'data' | 'scores' | {'auto'} ], governs type of rank test to perform.

- '
**data'**= single test on X-block (faster with smaller data blocks and more components), - '
**scores'**= test during regression on scores matrix (faster with larger data matricies), - '
**auto'**= automatic selection, or - '
**none'**= assumes X-block has sufficient rank.

- '

### See Also

crossval, modelstruct, pcr, pls, preprocess, nippls, analysis