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.
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