Here's a suggestion. The sample() function takes random samples of sets. See ?sample The set you want to take a random sample from is the rows of your data. Represent the rows by their row numbers. To get a vector of row numbers, you can use the seq() function. See ?seq
Let's suppose your data is in a data frame named 'mydat', and you want to introduce 10 instances of missing data. nr <- nrow(mydat) set.to.missing <- sample( seq(nr) , 10) mydat$Amount[set.to.missing] <- NA A simplified example of the core idea is: > foo <-seq(10) > foo [1] 1 2 3 4 5 6 7 8 9 10 > foo[3] <- NA> foo [1] 1 2 NA 4 5 6 7 8 9 10 -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 11/10/13 10:31 PM, "dila radi" <dilarad...@gmail.com> wrote: >Hi, > >Im new R users. In my research I use rainfall data and Im interested in >estimating missing data. I would like to use Normal Ratio Method to >estimate missing data. My problem is, how do I introduce missing data >randomly within my complete set of data? > > >Stn ID Year Mth Day Amount >48603 71 1 1 1 >48603 71 1 2 0.5 >48603 71 1 3 1.3 >48603 71 1 4 0.8 >48603 71 1 5 0 >48603 71 1 6 0 >48603 71 1 7 0 >... > >Thank you so much for your attention and help. > >Regards, >Dila > > [[alternative HTML version deleted]] > >______________________________________________ >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.
