[R] Forcing the intercept

[Heather Maughan]

Dear R-users:

I am doing multiple regressions using the "lm" function and would like to
force the intercept to be equal to a specific value (such as 4.3).  I was
able to find out how to force it through the origin but this does not work
for other values. 

I am also interested in forcing the regression parameters obtained from one
regression in another regression with a subset of the data.

Are either of these possible in R?  I have been searching the help guide for
hours and have been unsuccessful.

Many thanks,
Heather