[R] loess' robustness weights in loess

[Rafael A. Irizarry]

hi!

i want to change the "robustness weights" used by loess. these 
are described on page 316 of chambers and hastie's "statistical models in S" 
book as

r_i = B(e_i,6m)

where B is tukey's biweight function, e_i are the residulas, and m is the 
median average distance from 0 of the residuals. i want to 
change 6m to, say, 3m. 

is there a way to do this? i cant figure it out from the help files.

thanks,
rafael