I KNEW there was a better way! --- On Wed, 4/20/11, Jeremy Hetzel <jthet...@gmail.com> wrote:
> From: Jeremy Hetzel <jthet...@gmail.com> > Subject: Re: [R] Random Relabelling > To: r-help-arch...@googlegroups.com > Cc: r-help@r-project.org, "Kevin Matthews" <kevin-matth...@uiowa.edu> > Received: Wednesday, April 20, 2011, 2:25 PM > 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 <kevin-m...@uiowa.edu> > wrote: > > > > From: Kevin Matthews <kevin-m...@uiowa.edu> > > Subject: Re: [R] Random Relabelling > > To: "John Kane" <jrkr...@yahoo.ca> > > Cc: r-h...@r-project.org > > 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 <jrkr...@yahoo.ca> > 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 <kevin-m...@uiowa.edu> > wrote: > > > > > From: kmatthews <kevin-m...@uiowa.edu> > > > > > Subject: [R] Random Relabelling > > > > > To: r-h...@r-project.org > > > > > 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]] > > > > ______________________________________________ > > r-h...@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. > > > > > -----Inline Attachment Follows----- > > ______________________________________________ > 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. > ______________________________________________ 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.