On 09-May-09 16:10:42, Jacques Wagnor wrote: > Dear List, > When I plot a histogram with 'freq=FALSE' and overlay the > histogram with a normal pdf curve, everything looks as expected, > as follows: > > x <- rnorm(1000) > hist(x, freq=FALSE) > curve(dnorm(x), add=TRUE, col="blue") > > What do I need to do if I want to show the frequencies (freq=TRUE) > with the same normal pdf overlay, so that the plot would still look > the same? > > Regards, > Jacques
Think first about how you would convert the histogram densities (heights of the bars on the "density" scale) into histogram frequencies. Density * (bin width) * N = frequency where N = total number in sample. Then all you need to is multiply the Normal density by the same factor. To find out the bin width, take the difference between succesive values of the "breaks" component of the histogram. One way to do all this is N <- 1000 x <- rnorm(N) H <- hist(x, freq=TRUE) ## This will plot the histogram as well dx <- min(diff(H$breaks)) curve(N*dx*dnorm(x), add=TRUE, col="blue") Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 09-May-09 Time: 17:31:03 ------------------------------ 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 and provide commented, minimal, self-contained, reproducible code.