R/local.t.Student.R

In safe: Significance Analysis of Function and Expression

local.t.Student <-
function (X.mat, y.vec, ...)
{
    if (length(unique(y.vec)) > 2) {
        stop("local = \"t.Student\", but y.vec has more than 2 elements",
            call. = FALSE)
    }
    else if (!all(sort(unique(y.vec)) == c(0, 1))) {
        cat(paste("Warning: y.vec is not (0,1), thus Group 1 ==",
            y.vec[1], "\n"))
        y.vec <- (y.vec == y.vec[1]) * 1
    }
    return(function(data, vector = y.vec, ...) {
        x <- as.matrix(data[, vector == 1])
        y <- as.matrix(data[, !vector == 1])
        n.x <- dim(x)[[2]]
        n.y <- dim(y)[[2]]
        x.m <- x %*% rep(1/n.x, n.x)
        y.m <- y %*% rep(1/n.y, n.y)
        ssx <- (x^2 %*% rep(1, n.x) - x.m^2 * n.x)
        ssy <- (y^2 %*% rep(1, n.y) - y.m^2 * n.y)
        t <- (x.m - y.m)/sqrt((ssx + ssy) * (1/n.x + 1/n.y)/(n.x +
            n.y - 2))
        return(as.numeric(t))
    })
}