[R] starta.sampling with many (1000 times) and average them

[PIKAL Petr]

Hi

see in line

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Kristi Glover
> Sent: Friday, March 28, 2014 7:04 PM
> To: R-help
> Subject: [R] starta.sampling with many (1000 times) and average them
>
> 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

Use list object for test

test <- vector("list", 1000)

after that you can make a for cycle

for (i in 1:1000) {

test[[i]] <- strata.sampling(raw, 'group', 1)

}

>
> 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])

What is average? Mean? You want to average all values from those 3 columns from all tables to one number?

result <- 0
for (i in 1:1000) {
temp <- mean(as.matrix(test[[i]][,3:5]))
result <- temp + result
}
testA <- result/1000

Alternatively you can make one data frame from the list

test.d <- do.call(rbind, test)

and use aggregate, ave or other summary functions

> 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.

Please be more specific in your request. Final part is ambiguous.

Regards
Petr

>
> Thanks
>
>       [[alternative HTML version deleted]]
>
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