On Thu, Oct 8, 2009 at 4:26 PM, Monica Pisica <pisicandru@hotmail.com>wrote:

>
>  <fb7c7e870910080701o1683a41q7d4295d97af8cb25@mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
> MIME-Version: 1.0
>
>
> Hi=2C
> =20
> Thanks so much for your answer. It works beautifully for my example and of
> =
> course i will test it on the"real" data as well.
>

Just make sure, that it is choosing the right value - it might be that it is
choosing one to big or one to small (because of the diff()).


=20
> Thanks again=2C
>

Pleasure

Rainer


> =20
> Monica
> ________________________________
> > Date: Thu=2C 8 Oct 2009 16:01:36 +0200
> > Subject: Re: [R] intersection of 2 density curves
> > From: r.m.krug@gmail.com
> > To: pisicandru@hotmail.com
> > CC: r-help@stat.math.ethz.ch
> >
> >
> >
> > On Thu=2C Oct 8=2C 2009 at 3:48 PM=2C Monica Pisica> wrote:
> >
> >
> >
> >
> >
> > Hi=2C
> >
> >
> >
> > I would like to find out the coordinates of the intersection points of 2
> =
> density curves. I did a search but i didn't get any significant results. I
> =
> really hope some of you have some ideas. here it is an example:
> >
> >
> >
> > set.seed(123)
> >
> > x1 <- rnorm(100=2C 1=2C 1)
> >
> > x2 <- rnorm(100=2C 0=2C 1)
> >
> > d1 <- density(x1)
> >
> > d2 <- density(x2)
> >
> >
> >
> > plot(d1=2C col =3D 2)
> >
> > lines(d2=2C col =3D 4)
> >
> >
> >
> > if you specify n=2C from ant to in density() and keep them the same=2C
> th=
> en the density estimates are done for the same x-coordinates. Therefore
> you=
>  can compare d1$y with d2$y to deternine=2C where they intersect:
> >
> >
> > d2 <- density(x2=2C from=3D-3=2C to=3D5=2C n=3D2048)
> > d1 <- density(x1=2C from=3D-3=2C to=3D5=2C n=3D2048)
> > plot(d1=2C col =3D 2)
> > lines(d2=2C col =3D 4)
> > d1$y < d2$y
> > intersX <- d1$x[as.logical(abs(diff(d1$y < d2$y)))]
> >
> > intersY <- d1$y[as.logical(abs(diff(d1$y < d2$y)))]
> >
> > abline(v=3Dinters)
> > abline(h=3DintersY)
> >
> > Cheers=2C
> >
> > Rainer
> >
> >
> > Now i would like to know the coordinates of the intersection point. I
> did=
>  some "trial and error" and i come up with these .... (that means i did
> sev=
> eral vertical and horizontal lines through the graph until visually i
> "hit"=
>  the intersection point)
> >
> >
> >
> >
> > abline(v =3D 0.35=2C lty =3D 2)
> >
> > abline(h =3D 0.34=2C lty =3D 2)
> >
> >
> >
> > I really appreciate any hints you may have=2C thanks so much=2C
> >
> >
> >
> > Monica
> >
> > _________________________________________________________________
> >
> > Your E-mail and More On-the-Go. Get Windows Live Hotmail Free.
> >
> > http://clk.atdmt.com/GBL/go/171222985/direct/01/
> >
> > ______________________________________________
> >
> > 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.h=
> tml
> >
> > and provide commented=2C minimal=2C self-contained=2C reproducible code.
> >
> >
> >
> >
> > --
> > Rainer M. Krug=2C PhD (Conservation Ecology=2C SUN)=2C MSc (Conservation
> =
> Biology=2C UCT)=2C Dipl. Phys. (Germany)
> >
> > Centre of Excellence for Invasion Biology
> > Natural Sciences Building
> >
> > Office Suite 2039
> > Stellenbosch University
> > Main Campus=2C Merriman Avenue
> > Stellenbosch
> > South Africa
> >
> > Cell: +27 - (0)83 9479 042
> > Fax: +27 - (0)86 516 2782
> > Fax: +49 - (0)721 151 334 888
> >
> > email: Rainer@krugs.de
> >
> > Skype: RMkrug
> > Google: R.M.Krug@gmail.com
> >                                         =0A=
> _________________________________________________________________=0A=
> Your E-mail and More On-the-Go. Get Windows Live Hotmail Free.=0A=
> http://clk.atdmt.com/GBL/go/171222985/direct/01/=
>



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

Centre of Excellence for Invasion Biology
Natural Sciences Building
Office Suite 2039
Stellenbosch University
Main Campus, Merriman Avenue
Stellenbosch
South Africa

Cell:           +27 - (0)83 9479 042
Fax:            +27 - (0)86 516 2782
Fax:            +49 - (0)721 151 334 888
email:          Rainer@krugs.de

Skype:          RMkrug
Google:         R.M.Krug@gmail.com

	[[alternative HTML version deleted]]


