[R] Concatenation?

[Parkhurst, David]

If I have a vector of site abbreviations and a vector of depths in those water bodies, is there a simple way in R to combine them to make a third vector?
Examples:

site	depth		desired
MU	0		MU0
MU	1		MU1
MU	2		MU2
MC	0		MC0
MC	1		MC1
MC	2		MC2

The dataset has many more lines than this.  I can see how to do this with lots of if statements, but does R have magic that can make it happen easily?  I guess this would be called concatenation.