[R] proportional sampling

[tibi.codilean at ges.gla.ac.uk]

Dear All,

I wonder if you could help me.

I have a table with a series of sites that I would like to sample from.
The table has 5 columns:

ID
X Coordinate
Y Coordinate
Value
Factor


The conditions are that each site can be selected more than once and the
probability of it being selected (or sampled) is proportional to a factor
located in column 'Factor'

I am novice in terms of R, and am not entirely sure how to do the
proportional sampling.

Any help would be appreciated
Thanks
Tibi