Hi R Users,
I was trying to select a sample with columns (measured data) by stratum. I was
able to select rows by stratum. But, I wanted to repeat this procedures 1000
and want to take an average from the 1000 times. I think it is different than
bootstraping since I wanted to select (rondomly) row with many variable at a
time and repeat 1000 times then,average them.
#-----------------------------
I put here an example
raw=structure(list(watershed = structure(c(1L, 1L, 1L, 1L, 1L, 1L,
1L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("A", "B"), class = "factor"),
year = c(2001, 2001, 2002, 2002, 2002, 2002, 2002, 2001,
2001, 2001, 2002, 2002, 2002), sp1 = c(18.38, 29.1, 90.72,
16.12, 49.12, 20.81, 65.1, 1.87, 72.99, 93.45, 38.44, 67.13,
45.71), sp2 = c(46.46, 94, 86.87, 46.91, 21.41, 92.82, 87.75,
16.18, 18.16, 18.76, 19.26, 52.73, 49.09), sp3 = c(86.9,
62.82, 74.32, 75.49, 20.17, 58.84, 16.51, 44.14, 44.39, 32.36,
53.28, 67.42, 33.37)), .Names = c("watershed", "year", "sp1",
"sp2", "sp3"), class = "data.frame", row.names = c(NA, -13L))
raw$group<-paste(as.character(raw$watershed),as.character(raw$year), sep="|")
# strata.sampling -----
strata.sampling <- function(data, group,size, method = NULL) {
require(sampling)
if (is.null(method)) method <- "srswor"
if (!method %in% c("srswor", "srswr"))
stop('method must be "srswor" or "srswr"')
temp <- data[order(data[[group]]), ]
ifelse(length(size) > 1,
size <- size,
ifelse(size < 1,
size <- round(table(temp[group]) * size),
size <- rep(size, times=length(table(temp[group])))))
strat = strata(temp, stratanames = names(temp[group]),
size = size, method = method)
getdata(temp, strat)
}
#---------------
attach(raw)
test1<-strata.sampling(raw, 'group', 1)# select 1 row by watershed and year
test2<-strata.sampling(raw, 'group', 1)# select 1 row by watershed and year
test3<-strata.sampling(raw, 'group', 1)# select 1 row by watershed and year
test4<-strata.sampling(raw, 'group', 1)# select 1 row by watershed and year
...
...
...
# here I wanted to repeat this procedure 1000 times
test1000<-strata.sampling(raw, 'group', 2)# select 1 row by watershed and year
# and then average of this 1000 tables
testA<-average(test1[,3:5],test2[,3:5],test3[,3:5],.....test1000[,3:5])
Inform<-subset(test1, select=c(1,2,6,9)
FinalData<-data.frame(Inform, testA)
Would you give me some suggestion on how I can make a loop to repeat this
procedures and average them.
Thanks
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