[R] Complex sampling?
Daniel Nordlund
djnordlund at frontier.com
Wed Mar 9 23:23:58 CET 2011
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Hosack, Michael
> Sent: Wednesday, March 09, 2011 11:59 AM
> To: r-help at R-project.org
> Subject: Re: [R] Complex sampling?
>
>
>
> I want to thank everyone who offered advice for the assistance, but the
> responses so far have not taken into
> account that the sampling needs to progress through weeks, retaining
> information from one week to the next.
> I represented that retained information by a vector that when full is
> equal to 3:7 (i.e. DOW_NUMs). I know that
> this must be relatively simple for someone out there and I would really
> appreciate some help.
>
> Thank you,
>
> Mike
> From: ajmackey at gmail.com [mailto:ajmackey at gmail.com] On Behalf Of Aaron
> Mackey
> Sent: Wednesday, March 09, 2011 1:30 PM
> To: Hosack, Michael
> Cc: r-help at R-project.org
> Subject: Re: [R] Complex sampling?
>
> What I think you need is something along the lines of:
>
> matrix(c(sample(3:7), sample(3:7), sample(3:7), sample(3:7), ...), nrow=2)
>
> now, each column are your random pairs.
>
> -Aaron
> On Wed, Mar 9, 2011 at 1:01 PM, Hosack, Michael
> <mhosack at state.pa.us<mailto:mhosack at state.pa.us>> wrote:
> > -----Original Message-----
> > From: r-help-bounces at r-project.org<http://r-project.org> [mailto:r-
> help-bounces<mailto:r-help-bounces> at r-project.org<http://r-
> project.org>]
> > On Behalf Of Hosack, Michael
> > Sent: Wednesday, March 09, 2011 7:34 AM
> > To: r-help at R-project.org
> > Subject: [R] Complex sampling?
> >
> > R users,
> >
> > I am trying to generate a randomized weekday survey schedule that
> ensures
> > even coverage of weekdays in
> > the sample, where the distribution of variable DOW is random with
> respect
> > to WEEK. To accomplish this I need
> > to randomly sample without replacement two weekdays per week for each of
> > 27 weeks (only 5 are shown).
>
> This seems simple enough, sampling without replacement.
>
> However,
> > I need to sample from a sequence (3:7) that needs to be completely
> > depleted and replenished until the
> > final selection is made. Here is an example of what I want to do,
> > beginning at WEEK 1. I would prefer to do
> > this without using a loop, if possible.
> >
> > sample frame: [3,4,5,6,7] --> [4,5,6] --> [4],[1,2,3,(4),5,6] -->
> > [1,2,4,5,6] --> for each WEEK in dataframe
>
> OK, now you have me completely lost. Sorry, but I have no clue as to what
> you just did here. I looks like you are trying to describe some
> transformation/algorithm but I don't follow it.
>
>
>
> I could not reply to this email because it not been delivered to my inbox,
> so I had to copy it from the forum.
> I apologize for the confusion, this would take less than a minute to
> explain in conversation but an hour
> to explain well in print. Two DOW_NUMs will be selected randomly without
> replacement from the vector 3:7 for each WEEK. When this vector is reduced
> to a single integer that integer will be selected and the vector will be
> restored and a single integer will then be selected that differs from the
> prior selected integer (i.e. cannot sample the same day twice in the same
> week). This process will be repeated until two DOW_NUM have been assigned
> for each WEEK. That process is what I attempted to illustrate in my
> original message. This is beyond my current coding capabilities.
>
>
>
> >
> > Randomly sample 2 DOW_NUM without replacement from each WEEK ( () = no
> two
> > identical DOW_NUM can be sampled
> > in the same WEEK)
> >
> > sample = {3,7}, {5,6}, {4,3}, {1,5}, --> for each WEEK in dataframe
> >
>
> So, are you sampling from [3,4,5,6,7], or [1,2,4,5,6], or ...? Can you
> show an 'example' of what you would like to end up given your data below?
>
> >
> > Thanks you,
> >
> > Mike
> >
> >
> > DATE DOW DOW_NUM WEEK
> > 2 2011-05-02 Mon 3 1
> > 3 2011-05-03 Tue 4 1
> > 4 2011-05-04 Wed 5 1
> > 5 2011-05-05 Thu 6 1
> > 6 2011-05-06 Fri 7 1
> > 9 2011-05-09 Mon 3 2
> > 10 2011-05-10 Tue 4 2
> > 11 2011-05-11 Wed 5 2
> > 12 2011-05-12 Thu 6 2
> > 13 2011-05-13 Fri 7 2
> > 16 2011-05-16 Mon 3 3
> > 17 2011-05-17 Tue 4 3
> > 18 2011-05-18 Wed 5 3
> > 19 2011-05-19 Thu 6 3
> > 20 2011-05-20 Fri 7 3
> > 23 2011-05-23 Mon 3 4
> > 24 2011-05-24 Tue 4 4
> > 25 2011-05-25 Wed 5 4
> > 26 2011-05-26 Thu 6 4
> > 27 2011-05-27 Fri 7 4
> > 30 2011-05-30 Mon 3 5
> > 31 2011-05-31 Tue 4 5
> > 32 2011-06-01 Wed 5 5
> > 33 2011-06-02 Thu 6 5
> > 34 2011-06-03 Fri 7 5
> >
> > DF <-
> > structure(list(DATE = structure(c(15096, 15097, 15098, 15099,
> > 15100, 15103, 15104, 15105, 15106, 15107, 15110, 15111, 15112,
> > 15113, 15114, 15117, 15118, 15119, 15120, 15121, 15124, 15125,
> > 15126, 15127, 15128), class = "Date"), DOW = c("Mon", "Tue",
> > "Wed", "Thu", "Fri", "Mon", "Tue", "Wed", "Thu", "Fri", "Mon",
> > "Tue", "Wed", "Thu", "Fri", "Mon", "Tue", "Wed", "Thu", "Fri",
> > "Mon", "Tue", "Wed", "Thu", "Fri"), DOW_NUM = c(3, 4, 5, 6, 7,
> > 3, 4, 5, 6, 7, 3, 4, 5, 6, 7, 3, 4, 5, 6, 7, 3, 4, 5, 6, 7),
> > WEEK = c(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4,
> > 4, 4, 4, 4, 5, 5, 5, 5, 5)), .Names = c("DATE", "DOW", "DOW_NUM",
> > "WEEK"), row.names = c(2L, 3L, 4L, 5L, 6L, 9L, 10L, 11L, 12L,
> > 13L, 16L, 17L, 18L, 19L, 20L, 23L, 24L, 25L, 26L, 27L, 30L, 31L,
> > 32L, 33L, 34L), class = "data.frame")
> >
>
If I have missed a solution along the way, I apologize for the noise. I don't know if I completely understand yet, but maybe this will get the OP close to what is desired. If so, then I suspect someone can suggest a more efficient, R-ish way of doing this.
dow <- 3:7
s <- sample(dow)
for (i in 2:10) {
repeat{
tmp <- sample(dow)
if(tmp[5] != s[1]) break
}
s <- c(tmp,s)
}
pairs <- matrix(s,ncol=2,byrow=TRUE)
Hope this is helpful,
Dan
Daniel Nordlund
Bothell, WA USA
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