Densities allow you to then plot a reference distribution, or the result of a call to density, or other density based lines on top of your histogram and everything is appropriately scaled and is fairly easy.
-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Longe > Sent: Thursday, January 13, 2011 11:37 AM > To: r-help@r-project.org > Subject: [R] Question about histogram > > Dear list, > > I'm new to R, please bear with my silly questions. I'm trying to get > an > understanding of why the results I get from a call to hist() are not as > I thought I would get. When I use the parameter freq=FALSE, I think > the > plot will contain bars that none of them is larger than 1, because > they're probabilities. But for my code, the bars exceeded 1. > > The actual data seems immaterial. I tried with dummy data: > > > hist(runif(1000), freq=FALSE) > > and the histogram includes bars well over 1 in height. The man page > says that freq=FALSE produces densities, so that the total area is 1. > Clearly if all the values are between 0 and 1, as is the case here, > some > of the bars stand out above 1, for the area to be 1. I thought that it > is the sum of the bar heights that would be 1, so that the bars reflect > probabilities for each interval, rather than densities. So, the answer > to my question would be "because it's densities, not probabilities", > but > then the question is, why densities and not probabilities? > > Regards, > L. > > ______________________________________________ > 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.
