Regcon

Purpose

Converts a regression model to y = ax + b form.

Synopsis

[a,b] = regcon(mod)  % using REGRESSION model

[a,b] = regcon(regv,xmn,ymn)  % mean centered only

[a,b] = regcon(regv,xmn,ymn,xst,yst)  % mean centered and scaled

Description

regcon can be used to convert a model mod generated by the pcr, pls, or analysis functions, into a form expressed by the linear equation y = ax + b.

NOTES:

(1) regcon can only convert a regression model which uses Mean Centering, Autoscaling, or None as the preprocessing. Any other preprocessing will be rejected and cause an error.

(2) If the model was built with some variables excluded, regcon will infill with zeros as appropriate so that the output can be used on the original X-block with all variables present.

Alternatively, regcon can be used to convert the individual parts of a regression model, including the vector of regression coefficients regv and the means and scaling factors of the x- and y-block variables, to y = ax + b form.

Inputs

• mod = model structure that was generated by pls, pcr, or analysis

Alternatively, the following 5 individual parts of a regression model can be used as inputs:

• regv = column vector of regression coefficients
• xmn = predictor variable means
• ymn = predicted variable means
• xst = predictor variable scaling
• yst = predicted variable scaling

Note: If xmn or ymn is not supplied or is set equal to 0 or [], then it is assumed to be zero (i.e. no centering was used in the model). If xst or yst is not supplied or is set equal to 0 or [], then it is assumed to be one (i.e. no scaling was used in the model).

Outputs

• a = regression coefficients (a, in y = ax + b)
• b = intercept (b, in y = ax + b)

Notes

(1) REGCON can will convert a regression model which uses Mean Centering, Autoscaling, or None as the preprocessing. Any other preprocessing will be rejected and cause an error.

(2) If the model was built with some variables excluded, REGCON will infill with zeros as appropriate so that the output can be used on the original X-block with all variables present.

REGCON can also be used to convert the individual parts of a regression model, including the column vector of regression coefficients regv, predictor variable means xmn, predicted variable means ymn, predictor variable scaling xst, and predicted variable scaling yst. If xmn or ymn is not supplied or is set equal to 0 or [], then it is assumed to be zero (i.e. no centering was used in the model). If xst or yst is not supplied or is set equal to 0 or [], then it is assumed to be one (i.e. no scaling was used in the model). In this case the I/O syntax is:

[a,b] = regcon(regv,xmn,ymn,xst,yst)

Examples

[a,b] = regcon(mod); using REGRESSION model

[a,b] = regcon(regv,xmn,ymn); mean centered only

[a,b] = regcon(regv,xmn,ymn,xst,yst); mean centered and scaled

[a,b] = regcon(regv,xmn,ymn,[],yst); x data centered but not scaled

[a,b] = regcon(regv,0,0,xst,yst); x and y scaled by not centered

See Also

analysis, auto, mncn, modlpred, modlrder, pcr, pls, ridge