R/maintointer.R

In RAMP: Regularized Generalized Linear Models with Interaction Effects

maintointer <- function(mainIndex) {
    ### expand main effects to possible interaction effects output: a list of
    ### interaction effects
    aa = outer(mainIndex, mainIndex, f <- function(x, y) {
        paste("X", x, "X", y, sep = "")
    })
    aa[lower.tri(aa, diag = FALSE)] = NA
    bb = as.vector(aa)
    bb = bb[!is.na(bb)]
    return(bb)
}