It should also be remembered that there will often be multiple
intersections of such density estimates.
I hope this is not being done in support of a data-driven
discretization of two group comparisons. Such practices are to be
eschewed (as they are even worse than obfuscation).
--
David Winsemius.
On Oct 8, 2009, at 10:01 AM, Rainer M Krug wrote:
On Thu, Oct 8, 2009 at 3:48 PM, Monica Pisica
<pisican...@hotmail.com>wrote:
Hi,
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, 1, 1)
x2 <- rnorm(100, 0, 1)
d1 <- density(x1)
d2 <- density(x2)
plot(d1, col = 2)
lines(d2, col = 4)
if you specify n, from ant to in density() and keep them the same,
then the
density estimates are done for the same x-coordinates. Therefore you
can
compare d1$y with d2$y to deternine, where they intersect:
d2 <- density(x2, from=-3, to=5, n=2048)
d1 <- density(x1, from=-3, to=5, n=2048)
plot(d1, col = 2)
lines(d2, col = 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=inters)
abline(h=intersY)
Cheers,
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
several vertical and horizontal lines through the graph until
visually i
"hit" the intersection point)
abline(v = 0.35, lty = 2)
abline(h = 0.34, lty = 2)
I really appreciate any hints you may have, thanks so much,
Monica
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--
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
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email: rai...@krugs.de
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______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
