From: kmatthews <kevin-matthews_at_uiowa.edu>

Date: Mon, 25 Apr 2011 07:53:32 -0700 (PDT)

Date: Mon, 25 Apr 2011 07:53:32 -0700 (PDT)

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?

> 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_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 Mon 25 Apr 2011 - 14:55:45 GMT

Archive maintained by Robert King, hosted by
the discipline of
statistics at the
University of Newcastle,
Australia.

Archive generated by hypermail 2.2.0, at Tue 26 Apr 2011 - 00:50:33 GMT.

*
Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help.
Please read the posting
guide before posting to the list.
*