Question

I have data frame with two column say “a” and “b” now I want to create another column “c” which will take value 1 if the following condition satisfied:

a>x and within this subset b>y. x and y are arbitrary constant. The condition is somewhat nested. so if a>x returns 25 observation then b>y will search within that 25 observation NOT within entire data frame.

Answer 1

I really suspect you could have figured this out had you tried something…

R> x <- data.frame(a=1:10,b=10:1)
R> (x$c <- x$a > 3 & x$b > 4)
    a  b     c
1   1 10 FALSE
2   2  9 FALSE
3   3  8 FALSE
4   4  7  TRUE
5   5  6  TRUE
6   6  5  TRUE
7   7  4 FALSE
8   8  3 FALSE
9   9  2 FALSE
10 10  1 FALSE