ecdf
David is right. I am looking for the ecfd for fs$numstudents. The
other column is just an id.
I guess I don't know how to read the R documentation when it comes to functions.
looking at the documentation, i now notice that it says "Compute an
empirical cummulative distribution function and not a vector.
But still I would had assumed that in ecdf(x) ... the x is the argument.
So ecdf(fs$numstudents)(unique(fs$numstudents))
=============== ==================
function arguments
Yes? But I can't read that from the documentation? I suspect it has
something to those dots .... in the arguments which I don't
understand.
Why it says usage ecdf(x) when it's clearly not the case?
I don't get it.
Gawesh
On Sun, Oct 16, 2011 at 11:02 PM, David Winsemius
<dwinsemius at comcast.net> wrote:
On Oct 16, 2011, at 3:53 PM, Dennis Murphy wrote:
Hi: I don't understand what you're attempting to do. Wouldn't courseid be a categorical variable with a numeric label? If that is so, why are you trying to compute an EDF? An EDF computes cumulative relative frequency of a random variable, which by definition is numeric. If we were talking about EDFs for a distribution of student course grades on a numeric point system by course, that would make some sense, but I don't see how the course IDs themselves qualify as being on an interval scale of measurement. Could you clarify your intent?
Huh? gawesh asked for ecdf on numstrudents (not courseid) ?... pretty clearly a numeric value for which an ECDF should make sense. -- David. --
Dennis On Sun, Oct 16, 2011 at 8:31 AM, gj <gawesh at gmail.com> wrote:
Hi, Newbie here. I read the R for Beginners but i still don't get this. I have the following data (this is just an example) in a CSV file: ? courseid numstudents ? ? ? 101 ? ? ? ? 209 ? ? ? 141 ? ? ? ? ?13 ? ? ? 246 ? ? ? ? 140 ? ? ? 263 ? ? ? ? ? 8 ? ? ? 321 ? ? ? ? ?10 ? ? ? 361 ? ? ? ? ?10 ? ? ? 364 ? ? ? ? ?28 ? ? ? 365 ? ? ? ? ?25 ? ? ? 366 ? ? ? ? ?23 ? ? ? 367 ? ? ? ? ?34 I load my data using: fs<-read.csv(file="C:\\num_students_inallmodules.csv",header=T, sep=',') I want to get the ecdf. So, I looked at the ?ecdf which says usage:ecdf(x) So I expected ecdf(fs$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 at 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 at 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.
David Winsemius, MD Heritage Laboratories West Hartford, CT