Hi Tania, I think it could be. I tried a solution based on your data set using a chi-squared approach. Here is what I got:
# ---------------- # Data set set.seed(123) d <- data.frame(cbind(val=rnorm(1:10)^2, group=sample(LETTERS[1:5],100,repl=TRUE))) d[,"val"]<-as.numeric(as.character(d$val)) # Ranking "d" in decreasing order based on "val" and counting the number of observation in each group TABLE=table(d[order(val,decreasing=TRUE),][1:10,"group"]) TABLE A B C D E 3 2 3 1 1 # Chi-squared cht=chisq.test(TABLE) cht Chi-squared test for given probabilities data: TABLE X-squared = 2, df = 4, p-value = 0.7358 cht$p.value [1] 0.7357589 Hope this helps, Jorge On Tue, Apr 8, 2008 at 11:24 AM, Tania Oh <[EMAIL PROTECTED]> wrote: > Dear All, > > I do apologise if this question is out of place for this list but I've > tried searching mailing lists and read "Introductory Statistics with > R" by Peter Dalgaard, but couldn't find any hints on solving my > question below: > > I have a data frame (d) of values which I will rank in decreasing > order of "val". Each value belongs to a group, either 'A', 'B', 'C', > 'D', or 'E'. I then take the first 10 entries in data frame 'd' and > count the number of occurrences for each of the groups. I want to > test if certain groups occur more frequently than by chance in my > first 10 entries. Would a chi-square test or a hypergeometric test be > more suitable? If neither, what would be an alternative solution in > R? Below is my data: > > > ## data > L5 <- LETTERS[1:5] > d <- data.frame(cbind(val= rnorm(1:10)^2, group=sample(L5,100, > repl=TRUE))) > > str(d) > ##'data.frame': 100 obs. of 2 variables: > ##$ val : Factor w/ 10 levels "0.000169268449333046",..: 10 3 5 6 1 2 > 7 8 4 9 ... > ##$ group: Factor w/ 5 levels "A","B","C","D",..: 4 4 4 5 3 1 5 2 1 > 2 ... > > > Many thanks in advance and apologies again, > tania > > D. phil student > Department of Physiology, Anatomy and Genetics > University of Oxford > > ______________________________________________ > 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.
