lmdiag <- function(m1)
{
        if(length(class(m1)) == 0)
                stop("not a fitted model")
        if(class(m1) != "lm")
                stop("not an lm object")
        s <- summary(m1)$sigma
        lmi <- lm.influence(m1)
        e <- resid(m1)
        if(length(m1$weights) > 0)
                e <- e * sqrt(m1$weights)
        si <- lmi$sigma
        h <- lmi$hat
        g <- 1 - h
        k <- e/g^0.5
        isr <- k/s
        esr <- k/si
        pressi <- resid(m1)^2/(1 - h)^2
        dffits <- (h^0.5 * e)/(si * g)
        cooks <- (isr^2 * h)/(g * m1$rank)
        xx <- cbind(resid(m1), isr, esr, h, cooks, dffits,pressi)
        xx <- data.frame(xx)
        names(xx) <- c("resid", "int.stud", "ext.stud", "leverage", "cooks", 
                "dffits","press")
        xx
}