This function is slightly modified from rlm.default in the package MASS. The only difference is an option of "known.scale", which is an input vector of the same length of y.
# S3 method for cate
rlm(
x,
y,
weights,
...,
w = rep(1, nrow(x)),
init = "ls",
psi = psi.huber,
scale.est = c("MAD", "Huber", "proposal 2"),
k2 = 1.345,
method = c("M", "MM"),
wt.method = c("inv.var", "case"),
maxit = 100,
acc = 1e-04,
test.vec = "resid",
lqs.control = NULL,
known.scale = NULL
)