[R] subsetting

[Peter Hyde]

Hi!  I have never used this before, so please forgive my lack of proper
protocol...

Would someone please tell me how to subset a dataframe?

I have a table of data with x & y (spatial) coordinates, 2 attributes
(tree height and biomass) and a unique identification number for each
record

i have also created an array of random numbers equal to the number of
records in my data frame

i am trying to subset, in order to get the records that correspond to my
unique id numbers

basically, i am trying to figure out the equivalent to the "where" command
in IDL (which I understand is FORTRAN-like)

any insight would be greatly appreciated!!

thanks!