Dimitris Rizopoulos wrote:
Hi Mick,
regarding your first question try the following,
#if `x' is your data vector, then y <- seq(min(x), max(x), length=200) hist(x, prob=TRUE) lines(y, dnorm(y, mean(x), sd(x)))
Adding to this, what I do, a little bit simpler (?) is:
hist(x, prob=TRUE)
plot( function(y) dnorm(y, mean(x), sd(x)), from=min(x), to=max(x), col="red", add=TRUE)
Kjetil
regarding your second question, you'd probably want to fit a mixture model -> look at package `mclust'.
help(package="mclust")
I hope it helps.
Best, Dimitris
---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/16/396887 Fax: +32/16/337015 Web: http://www.med.kuleuven.ac.be/biostat/ http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
----- Original Message ----- From: "michael watson (IAH-C)" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, October 04, 2004 12:04 PM
Subject: [R] Help with normal distributions
Hi
I have two questions, the first perhaps dumber than the second.
Firstly, I have a data set, and when I plot a histogram it looks like a normal distribution. So I want to overlay a bell-shaped normal distribution on top of it, to demonstrate how similar it is to the normal distribution. I have read the help on dnorm(), rnorm(), pnorm() etc but still can't figure out how to plot a normal distribution. Any code would be appreciated....
Secondly, and perhaps more difficult, is a second data set. This, when plotted as a histogram, has two clear peaks, perhaps even three, all of which look as though they are normally distributed. So the theory is that my data set is actually made up of two, possibly three, underlying sub-sets of data which are normally distributed, but with different means and standard deviations. So 1) how do I test for this? And 2) how can I estimate the parameters (mean and SD) for the underlying distributions?
Thanks in advance for your help
Mick
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--
Kjetil Halvorsen.
Peace is the most effective weapon of mass construction.
-- Mahdi Elmandjra______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
