Hi Miao, With option freq=FALSE, the function hist calculates densities, i.e. in your case, counts/total/length in-between breaks.
h <- hist(Y1, breaks=seq(0, 350, by=35),freq=FALSE) If you calculate: h$counts/sum(h$counts)/35 = h$density Regards, Pascal ----- Mail original ----- De : jpm miao <miao...@gmail.com> À : r-help@r-project.org Cc : Envoyé le : Lundi 12 mars 2012 16h42 Objet : [R] A question on histogram - area much less than 1 Hello, I have problem running the histogram function "hist". The area under the histogram is much lower than 1. Could anyone tell me what the problem is? Thanks, (The total number of observation is 992 (close to 1000), so the probability that 0<Y1<35 is approximately 0.277) miao rm(list=ls()) par(mfrow=c(1, 1)) Y <- cbind(matrix(35*0.5,1,277), matrix(35*1.5, 1, 146), matrix(35*2.5, 1, 99), matrix(35*3.5,1,80), matrix(35*4.5, 1, 69), matrix(35*5.5, 1, 63), matrix(35*6.5, 1, 52), matrix(35*7.5,1, 53), matrix(35*8.5, 1, 55), matrix(35*9.5, 1, 98)) Y1<-as.vector(Y) par(mar=c(4.5, 4.1, 3.1, 0)) hist(Y1, breaks=seq(0, 350, by=35), ylim=c(0, 0.3), col="grey80", freq=FALSE) par(mar=c(5.1, 4.1, 4.1, 2.1)) [[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. ______________________________________________ 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.
