[R] plot problems

[Markus voigt]

Hello
I'm a newbie to the R program and I have problems to plot two functions 
in one plot window.
I know that I can use the plot command for the first function and the 
lines command for the second function but the problem is that the first 
function has only values beginnig from 1 to 7 on the x-axis and the 
second function values from 2 to 8. When I plot the second function with 
"lines" in the plot, it is drawn beginning at 1 and that is wrong 
because it should start at 2. Is there a parameter where you can define 
the start on the x-axis?
Thanks for help

Markus