[R] Fwd: my first post to the list

[Rodrigo Briceño]

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)
coefficients(mod)
}
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.
Thanks