With n = 100 I can see the two modes well separated in a density

plot.

However, I don't see why you cannot plot the density function, if

that's what you need:

curve(0.6 * dnorm(x, 0.4, 0.1) + 0.4 * dnorm(x, 0.8, 0.1), 0, 1.2)

Best,

Giovanni

> Date: Tue, 25 Aug 2009 13:55:26 +0100

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> > I'm trying to draw the density function of a mixed normal distribution

> > in the form of:

> > .6*N(.4,.1)+ .4*N(.8,.1)

> > At first I generate a random sample with size 200 by the below code:

> > means = c(.4,.8)

> > sds = sqrt(c(.1,.1))

> > ind = sample(1:2, n, replace=TRUE, prob=c(.6,.4))

> > x=rnorm(n,mean=means[ind],sd=sds[ind])

> >

> > Then I use the below code for drawing the graph:

> > plot(density(x))

> >

> > The plot doesn't seem to be belonging to the desired distribution,

> > because there is just one mode in it (I've seen the real graph of this

> > mixed normal in a paper, it has two clear distinct modes). Even the

> > hist() doesn't draw a plot similar to the real graph. I think the

> > generation code isn't correct. Is it? (I've asked the generation code

> > here!)

>

> The code is fine - the reason you can't see two peaks is that the two

> distributions overlap a lot. Set

> means <- c(.4, 10)

> to see double peaks more clearly.

>

> Regards,

> Richie.

>

> Mathematical Sciences Unit

> HSL

>

>

>

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