Re: [R] Conditional sampling

Thu, 10 Feb 2011 08:20:38 -0800 

On 10/02/2011 11:02 AM, Hosack, Michael wrote:

R experts,

I need to sample two rows without replacement from the following data frame 
such that
neither row contains the same 'DOW'. For example, I cannot select both a Monday 
morning
and a Monday afternoon. I am using STRATA_NUM as an index to randomly select 
rows from,
since this variable indexes all unique permutations of DOW, SITE, and TOD. I 
know how to
use the sample function to select rows, I just don't know how to sample with a 
constraint.
This seems simple, but I can't seem to find a simple solution. Any help would 
be greatly
appreciated.
I would use a rejection sampler, since your constraint is met for most samples. That is, sample without the constraint then 
throw away any samples that violate it.

Duncan Murdoch


Thank you,

Mike



DF<-
structure(list(DOW = structure(c(2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L,
5L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L), .Label = c("Fri", "Mon", "Thu", "Tue", "Wed"), class = "factor"),
     SITE = c(101L, 101L, 102L, 102L, 103L, 103L, 104L, 104L,
     101L, 101L, 102L, 102L, 103L, 103L, 104L, 104L, 101L, 101L,
     102L, 102L, 103L, 103L, 104L, 104L, 101L, 101L, 102L, 102L,
     103L, 103L, 104L, 104L, 101L, 101L, 102L, 102L, 103L, 103L,
     104L, 104L), TOD = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L,
     2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L,
     1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L,
     2L, 1L, 2L), .Label = c("Aftn", "Morn"), class = "factor"),
     STRATA_NUM = c(2L, 1L, 12L, 11L, 22L, 21L, 32L, 31L, 4L,
     3L, 14L, 13L, 24L, 23L, 34L, 33L, 6L, 5L, 16L, 15L, 26L,
     25L, 36L, 35L, 8L, 7L, 18L, 17L, 28L, 27L, 38L, 37L, 10L,
     9L, 20L, 19L, 30L, 29L, 40L, 39L), DATE = structure(c(1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
     3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L,
     4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L), .Label = c("5/3/2010",
     "5/4/2010", "5/5/2010", "5/6/2010", "5/7/2010"), class = "factor"),
     DOW_NUM = c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L,
     4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 6L, 6L, 6L,
     6L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L), WEEK = c(1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L)), .Names = c("DOW", "SITE",
"TOD", "STRATA_NUM", "DATE", "DOW_NUM", "WEEK"), class = "data.frame", 
row.names = c(NA,
-40L))

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Reply via email to