[R] Logical "and"

[Alexander Sokol]

Hello,

I have the following very simple problem:

Say I have two vectors,

a<-c(1,7,4,5,9,11)
b<-c(7,4,9)

I would like to create a vector containing the elements in a which are not in 
b.

Obviously, this is possible by writing

a[a!=b[1] & a!=b[2] & a!=b[3]]

But I would like a solution which is applicable to the situation where the 
number of elements in b is unknown.

I have looked in the R manuals, the FAQ and the mailing lists, but have been 
unable to find a solution.

Thank you for your replies,
 Alexander