Re: [R] Random Relabelling

From: John Kane <jrkrideau_at_yahoo.ca>
Date: Mon, 25 Apr 2011 16:54:33 -0700 (PDT)

> 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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