Displaying 1 result from an estimated 1 matches for "tp25873249p25886245".
2009 Oct 13
2
update.formula drop interaction terms
Dear R users,
How do I drop multiplication terms from a formula using update?
e.g.
forml=as.formula("Surv(time, status) ~ x1+x2+A*x3+A*x4+B*x5+strata(sex)")
#I would like to drop all instances of variable A (the main effect and its interactions). The following:
updated.forml=update(forml, ~ . -A)
#gives me this:
#Surv(time, status) ~ x1 + x2 + x3 + x4 + B + x5 + strata(sex) + A:x3 +