On 3/12/2010 3:06 PM, Hosack, Michael wrote: > Fellow R users, > > I am stumped on what would seem to be something fairly simple. > I have a dataframe that has a variable named 'WEEK' that takes > the numbers 1:26 (26 week time-period) with each number repeated > five times consecutively (once for each weekday, Monday through > Friday). Ex. 111112222233333.....2626262626. I would like to > randomly extract two weekdays per five day week for each of > 26 weeks and store this data as a separate dataframe. I have > been unable to get the sample function to work properly. > I have also tried using the runif function to assign random > numbers to each row of my dataframe, sort the dataframe first > by week number then by random number value, and finally select > the first two elements from each week subset (26 weeks total, > giving 52 randomly selected values). I can't figure out how > to select the first two elements. My goal is to randomly > select two weekdays per week (without replacement) for each of > 26 consecutive weeks. Any advice would be greatly appreciated.
DF <- data.frame(WEEK = rep(1:26, each=5), DAY = rep(1:5, 26), X = runif(5*26)) DF2 <- data.frame(DAY = c(replicate(26, sample(5, 2, replace=FALSE))), WEEK = rep(1:26, each=2)) new.DF <- merge(DF, DF2, all=FALSE) > Thank you, > > Mike > > ______________________________________________ > 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. -- Chuck Cleland, Ph.D. NDRI, Inc. (www.ndri.org) 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 512-0171 (M, W, F) fax: (917) 438-0894 ______________________________________________ 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.
