[R] only actual variable names in all.names()

[Vito Muggeo (UniPa)]

dear all,
When I use all.vars(), I am interest in extracting only the variable names..
Here a simple example

all.vars(as.formula(y~poly(x,k)+z))

returns
[1] "y" "x" "k" "z"

and I would like to obtain
"y" "x" "z"

Where is the trick?

many thanks
vito


-- 
====================================
Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Università di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 23895240
fax: 091 485726/485612
http://dssm.unipa.it/vmuggeo