Regresión escalonada

Selección de variables mediante regresión escalonada

Clases

GeneralizedLinearModel Generalized linear regression model class

`stepwiseglm`	Create generalized linear regression model by stepwise regression
`fitglm`	Create generalized linear regression model
`addTerms`	Add terms to generalized linear regression model
`removeTerms`	Remove terms from generalized linear regression model
`step`	Improve generalized linear regression model by adding or removing terms

Wilkinson notation provides a way to describe regression and repeated measures models without specifying coefficient values.