On Jul 27, 2011, at 5:36 AM, Rainer M Krug wrote:

Sorry for re-iterating - but are there any suggestions on how I could tackle
this problem?

You could start by providing an operational definition for "identity the areas where d.all is significantly larger then d.co and where it is significantly smaller" when presumably working from a perspective off not knowing anything about the parent distributions for the random draws. I had no notion of piecewise significance of differences in densities and figured you were the the one advancing the notion, so you should be defining what you meant. I was expecting one of my statistical betters to step in can correct or comment on the statistical issues, but that hasn't yet happened, so if you have an operational definition, we could try to implement it across the range of the two empiric densities.

--
David

Thanks,

Rainer

On Tue, Jul 26, 2011 at 2:58 PM, Rainer M Krug <[email protected]> wrote:

Hi

this might be a little bit off topic, but here it goes: lets assume I have
the following:

       set.seed(13)
       dat1 <- rnorm(2000, mean=10, sd=10)
       dat2 <- rnorm(100,  mean=10, sd=20)
       d.all <- density(dat, n=1024)
       d.co <-  density(x[[v]], , from=min(d.all$x), to=max(d.all$x),
n=1024)
       d.diff <- list(
                      x = d.all$x,
                      y = d.all$y - d.co$y
                      )

       ylim <- range(c(d.all$y, d.co$y, d.diff$y))
       plot(
            d.all,
            ylim = ylim
            )
       abline(h=0)
       lines(d.co, col="red")
       lines(d.diff$x, d.diff$y, col="blue")

Now I would like to identify the areas where d.all is significantly larger
then d.co and where it is significantly smaller.

What is the easiest approach to do this? At the moment I am not doing any tests, but I am sure there is a way to determine the ranges statistically?

Thanks,

Rainer

--
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      [email protected]

Skype:      RMkrug




--
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      [email protected]

Skype:      RMkrug

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