On Nov 25, 2009, at 7:51 PM, David Winsemius wrote:
Drats; Forgot the plot:
xx <- runif(100, -1, 1)
yy <- abs(xx)+rnorm(100,0,.2); plot(xx,yy, xlim=c( min(xx)-sd(xx),
max(xx)+sd(xx)), ylim =c( min(yy)-sd(yy), max(yy)+sd(yy)))
dens2 <- kde2d(xx, yy, lims=c(min(xx)-sd(xx), max(xx)+sd(xx),
min(yy)-sd(yy), max(yy)+sd(yy) ) )
contour(dens2, add=TRUE)
# You can pick a single contour if you like:
contour(dens2, level=0.05, col="red", add=TRUE)
contour(dens2, level=0.10, col="blue", add=TRUE)
And as a further note you can drop the bandwidth and lower the density
level to get a tighter fit:
xx <- runif(10000, -1, 1)
yy <- abs(xx)+rnorm(10000 ,0,.2); plot(xx,yy, xlim=c( min(xx)-
sd(xx), max(xx)+sd(xx)), ylim =c( min(yy)-sd(yy), max(yy)+sd(yy)),
cex=.2)
dens2 <- kde2d(xx, yy, lims=c(min(xx)-sd(xx), max(xx)+sd(xx), min(yy)-
sd(yy), max(yy)+sd(yy) ) , h=c(bandwidth.nrd(xx)/4, bandwidth.nrd(xx)/
4) )
contour(dens2, add=TRUE)
# You can pick a single contour if you like:
contour(dens2, level=0.05, col="red", add=TRUE)
contour(dens2, level=0.10, col="blue", add=TRUE)
contour(dens2, level=0.005, col="red", add=TRUE)
(More bat-like.)
--
David.
On Nov 25, 2009, at 7:46 PM, David Winsemius wrote:
This is not a true convave hull, but a 2D density is something
similar and perhaps more "statistical":
library(MASS)
xx <- runif(100, 0, 1)
xx <- runif(100, -1, 1)
yy <- abs(xx)+rnorm(100,0,.2)
dens2 <- kde2d(xx, yy, lims=c(min(xx)-sd(xx), max(xx)+sd(xx),
min(yy)-sd(yy), max(yy)+sd(yy) ) )
contour(dens2, add=TRUE)
# You can pick a single contour if you like:
contour(dens2, level=0.05, col="red", add=TRUE)
contour(dens2, level=0.10, col="blue", add=TRUE)
Happy Valentine's
--
David
On Nov 25, 2009, at 11:37 AM, Corrado wrote:
Dear friends,
Do you know how to calculate the CONCAVE hull of a set of points (2-
dimensional or n-dimensional)? is that possible in R? (With a
"smoothing"
parameter of course).
Best,
--
Corrado Topi
Global Climate Change & Biodiversity Indicators
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: ct...@york.ac.uk
______________________________________________
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.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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.html
and provide commented, minimal, self-contained, reproducible code.
