mma (version 10.8-1)

form.interaction: Create interaction terms of predictor(s) and potential moderator(s).

Description

Create interaction terms of predictor(S) and potential moderator(s). Mainly for linear models.

Usage

form.interaction(x,pred,inter.cov,predref=NULL,kx=NULL)

Value

Return a matrix with the interaction terms pred*inter.cov.

Arguments

x

As the x in data.org.

pred

The predictor(s) that might have interaction effect with the potential moderators.

inter.cov

The vector of names of potential moderators, which are included in x as covariates.

predref

The reference group of the predictor if the predictor is categorical.

kx

The interaction is with the kx-th predictor(s). kx can be a vector. If kx is null, the interaction is with each predictor.

Author

Qingzhao Yu

Details

form.interaction is used to create interaction terms between predictor(s) and potential moderator(s). The created interaction terms should be used as covariates in linear mediation analysis. The function is not needed for nonlinear mediation method.

See Also

"test.moderation", "moderate"

Examples

data("weight_behavior")
pred=data.frame(weight_behavior[,3])
names(pred)="pred"
x=weight_behavior[,c(2,4:14)]
inter=form.interaction(x,pred,inter.cov=c("sports","sweat"),predref=NULL) 
x=cbind(x,inter)
head(x)