Another option mydata <- rnorm(100000) mydata <- mydata[mydata>0] plot(density(c(mydata, -mydata), from=0))
If you want the area under the curve to be one, you'll need to double the density estimate dx <- density(c(mydata, -mydata), from=0) dx$y <- dx$y * 2 plot(dx) Chris Jeroen Ooms wrote: > > I am using density() to plot a density curves. However, one of my > variables is truncated at zero, but has most of its density around zero. I > would like to know how to plot this with the density function. > > The problem is that if I do this the regular way density(), values near > zero automatically get a very low value because there are no observed > values below zero. Furthermore there is some density below zero, although > there are no observed values below zero. > > This illustrated the problem: > > mydata <- rnorm(100000); > mydata <- mydata[mydata>0]; > plot(density(mydata)); > > the 'real' density is exactly the right half of a normal distribution, so > truncated at zero. However using the default options, the line seems to > decrease with a nice curve at the left, with some density below zero. This > is pretty confusing for the reader. I have tried to decrease the bw, masks > (but does not fix) some of the problem, but than also the rest of the > curve loses smoothness. I would like to make a plot of this data that > looks like the right half of a normal distribution, while keeping the > curve relatively smooth. > > Is there any way to specify this truncation in the density function, so > that it will only use the positive domain to calculate density? > -- View this message in context: http://www.nabble.com/plotting-density-for-truncated-distribution-tp20684995p20699699.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
