Hi Mike, please keep conversation on the list. Your code looks waaaay better now. I would not name the variable variances2 but that is just a matter of taste. What you could also do as a one-liner is something like
n <- 40 REPS <- 50000 mu <- 10 sigma <- 5 chisq <- replicate(REPS,(n-1)*var(rnorm(n,mu,sigma))/sigma^2) Try to draw a histogram of the variances2 or chisq values and superimpose the theoratical distribution. ?hist and ?curve might help. Best, kd ________________________________ Felad�: "Mike Brechb�hler" [osiri...@gmx.ch] K�ldve: 2015. �prilis 8. 0:28 To: Kehl D�niel T�rgy: Aw: RE: [R] Simulate values Hey Daniel, Thanks for your answer. I changed my commands and ended up with: matrix <- matrix(rnorm(500 * 40, 10, 5), ncol = 40, nrow = 500) variances1 <- apply(matrix, 1, var) variances2 <-(40 - 1) * variances1 / 25 What do you think about it? Does that work and was more or less what you expected to see? Best wishes, Mike Gesendet: Dienstag, 07. April 2015 um 05:39 Uhr Von: "Kehl D�niel" <ke...@ktk.pte.hu> An: Osiris10101 <osiri...@gmx.ch>, "r-help@r-project.org" <r-help@r-project.org> Betreff: RE: [R] Simulate values People do not usually do homework stuff here but I do not see the point in repeating the same sample 500 times. You might want to simulate 40x500 independent samples and put those in a matrix (see ?matrix) with lets say 40 rows and 500 columns. Once done, you can apply calculate the 500 sample standard deviations (or the chi-square values) where the ?apply function might help you. Lets start with that and lets see where you get. kd ________________________________________ Felad�: R-help [r-help-boun...@r-project.org] ; meghatalmazó: Osiris10101 [osiri...@gmx.ch] K�ldve: 2015. �prilis 7. 0:52 To: r-help@r-project.org T�rgy: [R] Simulate values Hello, I'm facing the following task: Simulate 500 values of the statistic (n-1)s^2/sigma^2 based on taking 500 samples of size n=40 from the N(mu=10; sigma^2 = 25) distribution. I think with the following command: rep(rnorm(40,10,25),times=500) I was able to simulate the samples but how I now can simulate the values of the chi-square-distribution is a mystery to me... I hope anyone can help me, shouldn't be a big problem... Thanks in advance! Reason for posting: I started a course at the University of Manchester and had to catch up with R, which I never used back in Switzerland. Now I'm solving some exercises to get more practice and this is one of them. -- View this message in context: http://r.789695.n4.nabble.com/Simulate-values-tp4705574.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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. [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
