[R] Fwd: my first post to the list

From: Rodrigo Briceņo <rjavierbriceno_at_gmail.com>
Date: Fri, 02 May 2008 13:12:10 -0600

Hello R-listers! My first post to the list is a very simple one for those who use the software continuosly. I am trying to understand the fixed-x resampling and random-x-resampling method proposed by Fox about Bootstrapping. The doubt that I have is on the side of the model run in one of the functions expressed for fixed-x resampling. What I don't understand is: X=model.matrix, and the -1 under mod= rlm. Please see below:
#fixed x-resampling
fit <- fitted(mod.duncan.hub)
e <- residuals(mod.duncan.hub)
X <- model.matrix(mod.duncan.hub)
boot.huber.fixed <- function(data, indices, maxit=20){ y <- fit + e[indices]
mod <- rlm(y ~ X - 1, maxit=maxit)
duncan.fix.boot <- boot(Duncan, boot.huber.fixed, 1999, maxit=100) duncan.fix.boot

I just need a quick explanation about WHAT the functions mean or do in this context.

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