Hi: I don't understand what you're attempting to do. Wouldn't courseid be a categorical variable with a numeric label? If that is so, why are you trying to compute an EDF? An EDF computes cumulative relative frequency of a random variable, which by definition is numeric. If we were talking about EDFs for a distribution of student course grades on a numeric point system by course, that would make some sense, but I don't see how the course IDs themselves qualify as being on an interval scale of measurement. Could you clarify your intent?
Dennis On Sun, Oct 16, 2011 at 8:31 AM, gj <gaw...@gmail.com> wrote: > Hi, > Newbie here. I read the R for Beginners but i still don't get this. > > I have the following data (this is just an example) in a CSV file: > > courseid numstudents > 101 209 > 141 13 > 246 140 > 263 8 > 321 10 > 361 10 > 364 28 > 365 25 > 366 23 > 367 34 > > I load my data using: > > fs<-read.csv(file="C:\\num_students_inallmodules.csv",header=T, sep=',') > > I want to get the ecdf. So, I looked at the ?ecdf which says usage:ecdf(x) > > So I expected ecdf(fs$numstudents) to work > > Instead it just returned: > Call: ecdf(fs$numstudents) > x[1:210] = 1, 2, 3, ..., 3717, 4538 > > After Googling, got this to work: > ecdf(fs$numstudents)(unique(fs$numstudents)) > > But I don't understand why if the ?ecdf says usage is ecdf(x) ... I > need to use ecdf(fs$numstudents)(unique(fs$numstudents)) to get this > to work? > > Can somebody explain this to me? > > Regards > Gawesh > > ______________________________________________ > 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.
