Dear Amelia, On 12/4/09, Amelia Livington <amelia_living...@yahoo.com> wrote: > > Dear R helpers > > Suppose I have two sets of ranges (interest rates) as > > Range 1 : (7 – 7.50, 7.50 – 8.50, 8.50 – 10.00) with respective > probabilities 0.42, 0.22 and 0.36. > > > Range II : (11-12, 12-14, 14-21) with respective probabilities 0.14, 0.56 > and 0.30 respectively. > > > My problem is to form the combinations of these ranges in a decreasing order > of joint probabilities. It is assumed that these ranges are independent. > > Suppose A represents (7-7.50), B represents (7.50-8.50) and C represents > (8.50 – 10.00). > Also let X be (11-12), Y is (12-14) and Z is (14-21). > > These two groups are independent i.e. Prob(A and Y) = P(A) * P(Y) > > So there are 9 combinations possible as (AX, AY, AZ, BX, BY, BZ, CX, CY and > CZ) respectively with the joint probabilities (0.059, 0.235, 0.126, 0.031, > 0.123, 0.066, 0.05, 0.202, 0.108) respectively. > > My problem is > (i) How to obtain these 9 combinations of > probabilities in the sense how do I obtain the various combinations of these > two ranges along-with their respective probabilities; > (ii) How to arrange these 9 probabilities in > descending order against the respective group combination i.e. for the > combination AY, the joint probability is maximum at 0.235, followed by CY at > 0.202 and so on. > > I sincerely apologize as perhaps I might not have raised the query properly. > I have become member of this group today only and its been hardly a week > since I have started learning R language. I have easily done this in Excel. > My output should be something like this – > > Combination Probability > AY 0.235 > CY 0.202 > AZ 0.126 > BY 0.123 > CZ 0.108 > BZ 0.066 > AX 0.059 > CX 0.050 > BX 0.031 > > > I request you to guide me. > > Thanking in advance > > Amelia >
This sounds like a homework problem, which is a strict no-no for this list; be sure to read the Posting Guide. I will give you the benefit of the doubt for now, but be warned for the future. Are you looking for something like the following? Probspace <- expand.grid(LETTERS[1:3], LETTERS[24:26]) marginals <- list() marginals[[1]] <- c(0.42, 0.22, 0.36) marginals[[2]] <- c(0.14, 0.56, 0.30) pdf <- expand.grid(marginals) Probspace$probs <- apply(pdf, 1, prod) # the joint pmf xtabs(probs ~ Var1 + Var2, data = Probspace) # sorted by probability Probspace[order(Probspace$probs), ] See the prob package for other utilities in this vein. You can make the labels better with c("7 – 7.50", "7.50 – 8.50", "8.50 – 10.00"), etc, in the first line instead of LETTERS. Welcome to R. Jay P.S. Please don't send HTML. Again, in the Posting Guide. > > [[alternative HTML version deleted]] > > *************************************************** G. Jay Kerns, Ph.D. Associate Professor Department of Mathematics & Statistics Youngstown State University Youngstown, OH 44555-0002 USA Office: 1035 Cushwa Hall Phone: (330) 941-3310 Office (voice mail) -3302 Department -3170 FAX VoIP: gjke...@ekiga.net E-mail: gke...@ysu.edu http://people.ysu.edu/~gkerns/ ______________________________________________ R-help@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.