Why don't you specifically tell hist what breaks to use: hist(x, breaks=seq(min(x), max(x), length=50), include.lowest=TRUE)
On Mon, May 19, 2008 at 5:31 AM, Ted Harding <[EMAIL PROTECTED]> wrote: > Hi Folks, > I'd like to know how hist() decides how many cells to use > when it ignores my "suggestion" to use say 'hist(...,breaks=50)'. > > More specifically, I have the results of 10000 simulations, > each returning an 8-vector, therefore 8 variables each with > 10000 values. Some of these 8 have somewhat skew distributions. > Say one of these 8 variables is X. > > I ask for H <- hist(X,breaks=50), and get a histogram which > usually has a different number of cells than what I intended. > > For instance, for one of these simulations, the 8 different > values of length(H$breaks) are: > > 70, 44, 38, 68, 50, 40, 46, 45 > > ?hist tells me > > A) > breaks: one of: > * a vector giving the breakpoints between histogram > cells, > * a single number giving the number of cells for the > histogram, > * a character string naming an algorithm to compute the > number of cells (see Details), > * a function to compute the number of cells. > > In the last three cases the number is a suggestion only. > > B) > The default for 'breaks' is '"Sturges"': see 'nclass.Sturges'. > > If I look at the code for nclass.Sturges() I see > > function (x) ceiling(log2(length(x)) + 1) > > and, for length(X) = 10000, this gives 15. This is not related > to any of the numbers of breaks I actually got, in any way obvious > to me. > > So: > Question 1: hist() has apparently ignored my "suggestion" of > "break=50". Why? What is the criterion for ignoring? > > Question 2: Presumably, if it ignores the "suggestion", it > does something else, of its choice. I would then, perhaps, > expect it to fall back to its default, which is (allegedly) > Sturges. But the result from nclass.Sturges looks different > from what it actually did. So what did it actually do, and > how did it decide on this? > > With thanks, > Ted. > > -------------------------------------------------------------------- > E-Mail: (Ted Harding) <[EMAIL PROTECTED]> > Fax-to-email: +44 (0)870 094 0861 > Date: 19-May-08 Time: 10:31:20 > ------------------------------ XFMail ------------------------------ > > ______________________________________________ > 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<http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? [[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.
