How to get values from dataframe's column conditional on other column

Hi to all members of this list,

I'm quite a novice to R and was wondering if there is a more elegant
way to solve a following problem:
Suppose we have a dataframe
  X     Y
.12   TRUE
-.24  TRUE
..     ...
.34   FALSE

i.e. two (or more columns) with data and we want to get vector of X
values conditional on Y values (say only X's when Y=TRUE).
Of course it is possible to do it by looping through the whole
dataframe, i was wondering if there is a a more elegant solution to
this in R?

You would do yourself a huge favour if you read the 'An Introduction to R'
manual distributed with R, or, for that matter, any of the other contributed  
introductory manuals on the R/CRAN site.

The answer, by the way, is 

    DF[ DF[,"Y"]==TRUE, "X" ]

ie you create a boolean condution for the rows (and == 'TRUE' could be
omitted if Y is boolean), and then select "X".  There are still issues that
may confuse you about data.frames collapsing to a single vector, please go
and read the manual. Really.

Dirk

Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison