From: jim holtman <jholtman_at_gmail.com>

Date: Thu, 03 Jul 2008 07:58:52 -0400

Date: Thu, 03 Jul 2008 07:58:52 -0400

You can use something like this to keep running your algorithm

# repeat until all values are positive

repeat{

x <- rnorm(10)

if (all(x >= 0)) break # conditions met; quit
}

On Thu, Jul 3, 2008 at 5:25 AM, Nadeem Shafique
<nadeemshafique_at_gmail.com> wrote:

> Respected All,

*>
**> I hope you are enjoying good health, I am tring to write a program in R but
**> could not be very sucessful. My program draws random sample form bivariate
**> normal distribution and then compute a variable PIJ. For certian samples
**> some entries of variable PIJ is apearing as negative, which result
**> in negative variance estimator. I want to introduce a loop in my program
**> that verify the each value of PIJ and if any value in PIJ is negitive return
**> back and draw another sample until a sample is selected that produces all
**> values of PIJ positive.
**>
**> library(mvtnorm)
**> library(combinat)
**> yg <- function(n,m,s) {
**> n<-10
**> m<-c(1,2)
**> s<- matrix(c(4,.2,.2,3), ncol=2)
**> x <- rmvnorm(n=n, mean=m, sigma=s)
**> pi <- x[,2]/sum(x[,2])
**> P <- pi*((1-2*pi)/(1-pi)+sum(pi/(1-pi)))
**> Pi<-t(combn(pi,2))
**> y<-t(combn(x[,1],2))
**> PI<-t(combn(P,2))
**> yht <- y[,1]/PI[,1]+ y[,2]/PI[,2]
**>
**> *PIJ <- (Pi[,1]*Pi[,2]*(2-Pi[,1]-Pi[,2]))/((1-Pi[,1])*(1-Pi[,2]))*
**>
**>
**> Eyht <- sum(yht*PIJ)
**> E2yht <- sum(yht^2*PIJ)
**> var1 <- E2yht - Eyht^2
**> var1
**> }
**> I want to impose the condition on PIJ(which is a vector). If any value in
**> the PIJ is negative then go back and take another sample until a sample is
**> selected which produces the PIJ positive(all values in PIJ).
**>
**> I hope now you can understand.
**>
**> Best Regards,
**>
**> Nadeem Shafique Butt
**>
**> [[alternative HTML version deleted]]
**>
**> ______________________________________________
**> R-help_at_r-project.org mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained, reproducible code.
**>
*

-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Thu 03 Jul 2008 - 12:13:06 GMT

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