That worked perfectly. Thank you Dennis - I very much appreciate the help!
Sara Maxwell, PhD, Postdoctoral Fellow Marine Conservation Institute University of California Santa Cruz Long Marine Laboratory 100 Shaffer Road Santa Cruz CA 95060 USA +1 206 355 3249 sara.maxw...@marine-conservation.org www.Marine-Conservation.org On May 25, 2011, at 12:58 PM, Dennis Murphy wrote: > Hi: > > Interesting problem. Here's one approach: > > library(plyr) > # Read in your datasets as data frames rather than matrices > dataset1 <- data.frame(id1 = rep(1:3, each = 10), > value1 = sample(seq_len(100), 30, replace = > TRUE)) > dataset2 <- data.frame(id2 = 1:3, subtract.value = c(1, 3, 5)) > > # The idea is to use the rows of dataset2 as parameters for > # subsetting and removing the first n_i rows. The tail() function > # serves the purpose: > foo <- function(id2, subtract.value) tail(subset(dataset1, id1 == > id2), -subtract.value) > > # Use the mdply function in the plyr package: >> mdply(dataset2, foo)[, -(1:2)] > id1 value1 > 1 1 2 > 2 1 55 > 3 1 18 > 4 1 4 > 5 1 3 > 6 1 76 > 7 1 74 > 8 1 21 > 9 1 97 > 10 2 19 > 11 2 49 > 12 2 20 > 13 2 73 > 14 2 79 > 15 2 95 > 16 2 52 > 17 3 60 > 18 3 58 > 19 3 68 > 20 3 59 > 21 3 13 > > > HTH, > Dennis > > On Wed, May 25, 2011 at 9:55 AM, Sara Maxwell <smaxw...@ucsc.edu> > wrote: >> Dear R users, >> >> I have two datasets: >> >> id1 <- c(rep(1,10), rep(2,10), rep(3,10)) >> value1 <- sample(1:100, 30, replace=TRUE) >> dataset1 <- cbind(id1,value1) >> >> id2 <- c(1,2,3) >> subtract.value <- c(1,3,5) >> dataset2 <- cbind(id2, subtract.value) >> >> I want to subtract the number of rows in the subtract.value that >> corresponds to the id value in dataset1. So for the 1 in id1, I want >> to remove the first row, for 2 in id1 I want to remove the first 3 >> rows, for 3 in id1 I want to remove the first 5 rows, finally >> creating >> a new dataframe with the remaining values. >> >> I am having trouble structuring a loop that can do this by the unique >> ids in the first dataset while matching the ids in the datasets. >> >> Any thoughts would be greatly appreciated. >> >> Thank you, >> Sara >> >> >> [[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. >> [[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.
