From: John Kane <jrkrideau_at_yahoo.ca>

Date: Mon, 25 Apr 2011 16:54:33 -0700 (PDT)

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 Tue 26 Apr 2011 - 00:03:20 GMT

Date: Mon, 25 Apr 2011 16:54:33 -0700 (PDT)

- On Mon, 4/25/11, kmatthews <kevin-matthews_at_uiowa.edu> wrote:

*> From: kmatthews <kevin-matthews_at_uiowa.edu>
**> Subject: Re: [R] Random Relabelling
*

> To: r-help@r-project.org

*> Received: Monday, April 25, 2011, 10:53 AM
**> 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?
*

Certainly and thanks

*>
*

> On Wed, Apr 20, 2011 at 1:26 PM, jthetzel [via R] <

*> ml-node+3463799-950416470-231689_at_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
**> >
**> >
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