[R-sig-Geo] GRTS sampling

[ONKELINX, Thierry]

Dear all,

I have put the code that I've posted before into a package. The package is available on R-forge.

install.packages("GRTS", repos="http://R-Forge.R-project.org")

Any comments are welcome.

Best regards,

Thierry

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium
+ 32 2 525 02 51
+ 32 54 43 61 85
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey



On Mon, Feb 11, 2013 at 6:45 AM, Dick Brus <dick.brus at wur.nl> wrote:

> I try to understand the hierarchical randomization as applied in the
> GRTS design.
>
> I randomized 16 points on a square grid, see R script below. The
> argument do.sample was set to FALSE, so that the result consists of a
> dataframe of all 16 points instead of a GRTS sample. When plotting the
> order of the points it appears that the numbers 1-4 are not always in
> different subsquares (of which there are four) , for instance points 1
> and 3 are both in the lower-right subsquare. What am I doing wrong?
>
> library(spsurvey)
>
> frame<-expand.grid(x=seq(from=1,to=4,by=1),y=seq(from=1,to=4,by=1))
>
> #population size (total number of sampling units in Kandahar)
> N<-nrow(frame)
>
> #set number of sampling units (sample size) to be selected
> n<-4
>
> design<-list(None=list(panel=c(Panel1=n), seltype="Equal",
> caty.n=c("Caty 1"=n), over=0)) x<-frame$x y<-frame$y index<-1:N
> att<-data.frame(x=x,y=y,ids=index)
>
> #do.sample=FALSE gives all sampling units in hierarchical? randomized
> order res<-grts(design, DesignID="Site", SiteBegin=1, type.frame="finite",
>          src.frame="att.frame", in.shape=NULL, sp.object=NULL,
> att.frame=att,
>          id=NULL, xcoord="x", ycoord="y", stratum=NULL, mdcaty=NULL,
> startlev=2,
>          maxlev=11, maxtry=1000, shift.grid=FALSE,
> do.sample=rep(FALSE, length(design)),
>          shapefile=FALSE, prjfilename=NULL, out.shape="sample")
> frame.randomized<-data.frame(res$xcoord,res$ycoord)
> names(frame.randomized)<-c("x","y")
> frame.randomized$id<-1:N
>
> png(file = "GRTSRandomizedFrameSquare.png", width = 480, height = 480)
> print(
>   ggplot(data = frame.randomized) +
>     geom_text(
>       data = frame.randomized,
>       mapping = aes(
>         x = x,
>         y = y,
>         label = id
>       ),
>       size = 5
>     ) +
>     coord_equal()
> )
> dev.off()
>
> <
> http://r-sig-geo.2731867.n2.nabble.com/file/n7582569/GRTSRandomizedFra
> meSquare.png
> >
>
>
>
> --
> View this message in context:
> http://r-sig-geo.2731867.n2.nabble.com/GRTS-sampling-tp7582569.html
> Sent from the R-sig-geo mailing list archive at Nabble.com.
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
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>

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