[R] Problem in applying if statment

[Nadeem Shafique]

Respected All,

I am writing a program in R and facing some problem with applying "if statment".

Program first draw random numbers from bivariate normal distribution
         then compute variable say Pi and Pij from that sample and
then further computation
......
.....
.....
In some samples Pij is appearing with negitive sign and ultimately
resulted in an negative variance estimator.  Now i want to design the
program like this if the Pij is negative then go back and draw another
sample until we get a sample that produces positive Pij and then move
forward for further processing.

Best Regards,

Nadeem Shafique Butt