Thanks to everyone... this helps a lot. Just a quick question about etiquette in this forum (as it my first time questioning)... are notes of gratitude usually given in these forums?
On Wed, Apr 20, 2011 at 1:26 PM, jthetzel [via R] < ml-node+3463799-950416470-231...@n4.nabble.com> wrote: > Kevin, > > The following follows John's suggestion, but without the loop. It's quick > for me. > > Jeremy > > > Jeremy T. Hetzel > Boston University > > > > ## Generate sample data > n <- 4000 > rep <- 1000 > rate <- rnorm(n, mean = 15, sd = 2) / 100000 # Mortality rates around > 15/100k > > ## Create an empty matrix with appropriate dimensions > permutations <- matrix(ncol = n, nrow = rep) > > ## Use apply() to resample > permutations <- apply(permutations, 1, function(x) > { > sample(rate, size = n, replace = F) > }) > > ## Look at the matrix > dim(permutations) > head(permutations) > > ## Find the column means > means <- apply(permutations, 1, mean) > means > > > > > > On Wednesday, April 20, 2011 1:56:35 PM UTC-4, John Kane wrote: > > > > > There is probably a better way to do this but a for loop like this should > > > work. You would just need to change the numbers to yours and then add on > the > > locations > > ========================================================= > > > > scores <- 1:5 > > mydata <- matrix(data=NA, nrow=5, ncol=10) > > > > for(i in 1:10) { > > mydata[,i] <- sample(scores, 5, replace=FALSE) > > } > > > > ========================================================= > > --- On Wed, 4/20/11, Kevin Matthews <[hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=0&by-user=t>> > wrote: > > > > From: Kevin Matthews <[hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=1&by-user=t>> > > > Subject: Re: [R] Random Relabelling > > To: "John Kane" <[hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=2&by-user=t>> > > > Cc: [hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=3&by-user=t> > > Received: Wednesday, April 20, 2011, 1:22 PM > > > > I have a map of Iowa of with 4000 locations. At each location, I have a > > cancer mortality rate. I need to test my null hypothesis; that the > spatial > > distribution of the mortality rates is random. For this test, I need to > > > establish a spatial reference distribution. > > > > > > My reference distribution will be created by some random relabelling > > algorithm. The 4000 locations would remain fixed, but the observed > > mortality rates would be randomly redistributed. Then, I want 1000 > > permutations of the same algorithm. For each of those 1000 times, I > would > > record the redistributed mortality rate at each location. Then, I would > > > calculate the mean of the 1000 points. The result would be a spatial > > reference distribution with a mean value of the random permutations at > each > > of the 4000 locations. > > > > Thanks for the response,Kevin > > > > On Wed, Apr 20, 2011 at 11:08 AM, John Kane <[hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=4&by-user=t>> > wrote: > > > > > > Can you explain this a bit more. At the moment I don't see what you are > > trying to achieve. "calculate the mean of the 1000 values at each of > the > > 4000 points" does not seem to make sense. > > > > --- On Wed, 4/20/11, kmatthews <[hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=5&by-user=t>> > wrote: > > > > > From: kmatthews <[hidden > > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=6&by-user=t>> > > > > > > Subject: [R] Random Relabelling > > > > > To: [hidden > > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=7&by-user=t> > > > > > Received: Wednesday, April 20, 2011, 10:04 AM > > > > > I have 4000 observations that I need > > > > > to randomly relabel 1000 times and then > > > > > calculate the mean of the 1000 values at each of the 4000 > > > > > points. Any ideas > > > > > for where to begin? > > > > > > > > > > Thanks > > > > > Kevin > > > > > > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > [hidden > > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=8&by-user=t>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. > > > > > ______________________________________________ > [hidden > email]<http://user/SendEmail.jtp?type=node&node=3463799&i=9&by-user=t>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. > Jeremy T. Hetzel > Boston University > > > ------------------------------ > If you reply to this email, your message will be added to the discussion > below: > http://r.789695.n4.nabble.com/Random-Relabelling-tp3463100p3463799.html > To unsubscribe from Random Relabelling, click > here<http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=3463100&code=a2V2aW4tbWF0dGhld3NAdWlvd2EuZWR1fDM0NjMxMDB8MTg3NTE4Mzk1OA==>. > > -- View this message in context: http://r.789695.n4.nabble.com/Random-Relabelling-tp3463100p3473298.html Sent from the R help mailing list archive at Nabble.com. [[alternative HTML version deleted]] ______________________________________________ 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.