Agriculture Reference
In-Depth Information
Fig. 6.1
n
¼100 units selected from
N
¼1,000 with a simple random sampling without replace-
ment scheme
12345
200 200 200 200 200
>
framepop
<
- cbind(framepop,yobs,q1obs,q2obs)
The most widely used
R
package for pseudo-randomly
1
selecting a sample is
sampling
. It is a collection of sampling algorithms that were described in Till´
(
2006
). The SRS function is
srswor
, and is used in this example to select
n
100
units without replacement (see Fig.
6.1
). The outcome of this function is a vector of
size
N,
which is an indicator variable equal to 1 if the unit is selected, and 0 otherwise:
¼
>
par(mar
¼
c(1,1,1,1),xaxs
¼
"i",yaxs
¼
"i")
>
plot(framepop$xc,framepop$yc, axes
¼
F,cex
¼
0.5,
+
pch
¼
19,xlim
¼
c(0,1),ylim
¼
c(0,1))
>
box()
>
set.seed(200694)
>
srs
<
- srswor(n,N)
>
table(srs)
srs
01
900 100
>
framesrs
<
- framepop[srs
¼¼
1,]
>
points(framesrs$xc,framesrs$yc, pch
¼
1, cex
¼
2)
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