[R] rlm results on trellis plot

[deepayan.sarkar at gmail.com]

On 6/7/07, Alan S Barnett <asb at mail.nih.gov> wrote:
> How do I add to a trellis plot the best fit line from a robust fit? I
> can use panel.lm to add a least squares fit, but there is no panel.rlm
> function.

Well, panel.lmline (not panel.lm, BTW) is defined as:

> panel.lmline
function (x, y, ...)
{
    if (length(x) > 0)
        panel.abline(lm(as.numeric(y) ~ as.numeric(x)), ...)
}

So it's not much of a stretch to define

panel.rlmline <- function(x, y, ...)
    if (require(MASS) && length(x) > 0)
        panel.abline(rlm(as.numeric(y) ~ as.numeric(x)), ...)

The other replies have already shown you how you might use this in a call.

-Deepayan