[R] Creating a new table from a set of constraints

[Francisco J. Bido]

Hi Everyone,

Here's a silly newbie question.  How do I remove unwanted rows from an 
R table?  Say that I read my data as:

X <- read.table("mydata.txt")

and say that there are columns for age and gender.  Call these X[5] and 
X[10], respectively.
Here, X[5]  is a column of positive integers and X[10] is binary valued 
i.e., zero (for male) and one (for female)

Now, say that I want to form a new table called Y which has the 
following constraints:

1.  Only females that are between 18 and 40 years old.
2.  Only males that are between 20 and 30 years old

I can do this using a typical procedural approach (no different than C 
programmer would) but it seems
to me that R has many shortcuts and so I thought I ask first before 
heading on an inefficient path. What's
a good way of doing this, my data set is very large?

Thanks,
-Francisco