plot.lm.x <<- 
function (x, which = 1:4, caption = c("Residuals vs Fitted", 
    "Normal Q-Q plot", "Scale-Location plot", "Cook's distance plot"), 
    panel = points, sub.caption = deparse(x$call), main = "", 
    ask = prod(par("mfcol")) < length(which) && dev.interactive(), 
    ..., id.n = 3, labels.id = names(residuals(x)), cex.id = 0.75) 
{
    if (!inherits(x, "lm")) 
        stop("Use only with 'lm' objects")
    show <- rep(FALSE, 4)
    if (!is.numeric(which) || any(which < 1) || any(which > 4)) 
        stop("`which' must be in 1:4")
    show[which] <- TRUE
    r <- residuals(x)
    n <- length(r)
    yh <- predict(x)
    if (any(show[2:4])) 
        s <- if (inherits(x, "rlm")) 
            x$s
        else sqrt(deviance(x)/df.residual(x))
    if (any(show[2:3])) {
        ylab23 <- if (inherits(x, "glm")) 
            "Std. deviance resid."
        else "Standardized residuals"
        hii <- lm.influence(x)$hat
        w <- weights(x)
        r.w <- if (is.null(w)) 
            r
        else (sqrt(w) * r)[w != 0]
        rs <- r.w/(s * sqrt(1 - hii))
    }
    if (any(show[c(1, 3)])) 
        l.fit <- if (inherits(x, "glm")) 
            "Predicted values"
        else "Fitted values"
    if (is.null(id.n)) 
        id.n <- 0
    else {
        id.n <- as.integer(id.n)
        if (id.n < 0 || id.n > n) 
            stop(paste("`id.n' must be in { 1,..,", n, "}"))
    }
    if (id.n > 0) {
        if (is.null(labels.id)) 
            labels.id <- paste(1:n)
        iid <- 1:id.n
        show.r <- order(-abs(r))[iid]
        if (any(show[2:3])) 
            show.rs <- order(-abs(rs))[iid]
        text.id <- function(x, y, ind, adj.x = FALSE) text(x - 
            if (adj.x) 
                strwidth(" ") * cex.id
            else 0, y, labels.id[ind], cex = cex.id, xpd = TRUE, 
            adj = if (adj.x) 
                1)
    }
    one.fig <- prod(par("mfcol")) == 1
    if (ask) {
        op <- par(ask = TRUE)
        on.exit(par(op))
    }
    if (show[1]) {
        ylim <- range(r, na.rm = TRUE)
        if (id.n > 0) 
            ylim <- ylim + c(-1, 1) * 0.08 * diff(ylim)
        plot(yh, r, xlab = l.fit, ylab = "Residuals", main = main, 
            ylim = ylim, type = "n", ...)
        panel(yh, r, ...)
        if (one.fig) 
            title(sub = sub.caption, ...)
        mtext(caption[1], 3, 0.25)
        if (id.n > 0) {
            y.id <- r[show.r]
            y.id[y.id < 0] <- y.id[y.id < 0] - strheight(" ")/3
            text.id(yh[show.r], y.id, show.r, adj.x = TRUE)
        }
        abline(h = 0, lty = 3, col = "gray")
    }
    if (show[2]) {
        ylim <- range(rs, na.rm = TRUE)
        ylim[2] <- ylim[2] + diff(ylim) * 0.075
        qq <- qqnorm(rs, main = main, ylab = ylab23, ylim = ylim, 
            ...)
        if (one.fig) 
            title(sub = sub.caption, ...)
        mtext(caption[2], 3, 0.25)
        if (id.n > 0) 
            text.id(qq$x[show.rs], qq$y[show.rs], show.rs, adj.x = TRUE)
    }
    if (show[3]) {
        sqrtabsr <- sqrt(abs(rs))
        ylim <- c(0, max(sqrtabsr, na.rm = TRUE))
        yl <- as.expression(substitute(sqrt(abs(YL)), list(YL = as.name(ylab23))))
        yhn0 <- if (is.null(w)) 
            yh
        else yh[w != 0]
        plot(yhn0, sqrtabsr, xlab = l.fit, ylab = yl, main = main, 
            ylim = ylim, type = "n", ...)
        lines(lowess(yhn0, sqrtabsr))
        panel(yhn0, sqrtabsr, ...)
        if (one.fig) 
            title(sub = sub.caption, ...)
        mtext(caption[3], 3, 0.25)
        if (id.n > 0) 
            text.id(yhn0[show.rs], sqrtabsr[show.rs], show.rs, 
                adj.x = TRUE)
    }
    if (show[4]) {
        cook <- cooks.distance(x, sd = s, res = r)
        if (id.n > 0) {
            show.r <- order(-cook)[iid]
            ymx <- cook[show.r[1]] * 1.075
        }
        else ymx <- max(cook)
        plot(cook, type = "h", ylim = c(0, ymx), main = main, 
            xlab = "Obs. number", ylab = "Cook's distance", ...)
        if (one.fig) 
            title(sub = sub.caption, ...)
        mtext(caption[4], 3, 0.25)
        if (id.n > 0) 
            text.id(show.r, cook[show.r] + 0.4 * cex.id * strheight(" "), 
                show.r)
    }
    if (!one.fig && par("oma")[3] >= 1) 
        mtext(sub.caption, outer = TRUE, cex = 1.25)
    invisible()
}