Displaying 20 results from an estimated 1000 matches similar to: "Concave Hull"
2006 May 02
2
Concave Hull?
I am modeling a trend surface using trmat and want to trim the resulting matrix to the area enclosed by my real data (i.e., remove all the extrapolated areas). I was using chull and in.chull to calculate the convex hull and change all the other values created by trmat to NA. However, my real data has portions that are slightly concave so chull would give me slivers that are extrapolations from
2009 Nov 25
3
Concave hull
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: ct529 at york.ac.uk
2009 Nov 24
2
convex hull for cluster analysis
Dear R gurus and users,
I seem to have problem finding the right tool for plotting convex hulls over
2D plots, after a cluster analysis. In fact I would like to draw a convex hull
in 2D for a generic group of points. I found a "convhulln", but this doesn't seem
to give me a convex hull. Here is what I do:
> library(mvtnorm)
> Mean <- c(2,1)
> Sigma <-
2007 Mar 24
2
sampling from the unoform distrubuton over a convex hull
Dear list,
Does anyone have a suggestion (or better still) code for sampling from the uniform distribution over the convex hull of a set of points?
Many thanks and best wishes,
Ranjan
2001 Dec 10
1
high dimensional convex hull
Does anyone know of a R package that will determine the convex hull of a
high-dimensional dataset (say 4-10 dimensions). I know chull works for
2D data.
I'm neophyte to R and convex hulls so please keep it simple.
Many thanks
Ben
--
Ben Stapley.
Biomolecular Sciences, UMIST, PO Box 88, Manchester M60 1QD.
Tel 0161 200 5818
Fax 0161 236 0409
2009 Jan 25
3
Using help()
Dear R-helpers,
I wonder if you can give me advice about the best way to use help().
(1) If I type ?normal because I forgot the name dnorm() I get a long
list of relevant pages. Getting to right page is laborious.
(2) If I remember dnorm() and want to be reminded of the call, I also
get a list of pages.
Advice?
It seems to me that if the output of help() listed base functions
first, it
2009 Jan 31
1
Extracting coordinates for cluster::clusplot()
Dear Friends,
require(cluster)
x <- rbind(cbind(rnorm(10, 0, 0.5), rnorm(10, 0, 0.5)),
cbind(rnorm(15, 5, 0.5), rnorm(15, 5, 0.5)))
plot(pp <- pam(x, 2), which.plots = 1)
How can I extract the coordinates used in the plot?
_____________________________
Professor Michael Kubovy
University of Virginia
Department of Psychology
Postal Address:
P.O.Box 400400, Charlottesville, VA 22904-4400
2009 Mar 21
1
Calling R from Java (trying the R interface to Omegahat and Java)
Dear R-helpers,
I run R version 2.8.1 (2008-12-22) on i386-apple-darwin8.11.1
I would like to call R from Java. I downloaded SJava_0.69-0.tar.gz,
and then issued the command suggested on http://www.omegahat.org/
RSJava/ :
% R INSTALL -c SJava_0.69-0.tar.gz
ARGUMENT 'INSTALL' __ignored__
WARNING: unknown option '-c'
ARGUMENT 'SJava_0.69-0.tar.gz' __ignored__
I then
2007 Sep 07
1
Finding convex hull?
Dear UseRs,
I would like to know which function is the most efficient in finding
convex hull of points in 3(or 2)-dimensional case?
Functions for finding convex hull is the following:
convex.hull (tripack), chull (grDevices), in.chull (sgeostat),
convhulln (geometry), convexhull.xy (spatstat), calcConvexHull
(PBSmapping).
I also would like to know if there is a function that can be used
2001 Sep 22
2
Finding a 3D convex hull in R
Dear List Members,
I'm presently carrying out morphological analysis of a data set of neuronal
structures. These are essentially 3D binary trees. In due course I will be
trying to use discriminant analysis or other methods to classify these
neurons based on morphological variables such as total tree length, segment
number etc.
I would like to calculate a 3D convex hull for a set of X,Y,Z
1999 Aug 30
1
convex hulls
Does anybody know if there are functions to:
1. Define a convex hull on a space with more
than 2 dimensions? chull just works for a plane.
2. Numerically select elements within a given complex
hull.
Thanks!
Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 93409 5410
fax 34 93411 0012
alobo at ija.csic.es
2009 Jan 24
1
Help with dudi.pca
Dear R-helpers,
I have two data frames, op and em4:
> str(op)
'data.frame': 37 obs. of 5 variables:
$ m : num 0.202 0.336 0.122 0.139 0.14 ...
$ lln : num 0.798 0.643 0.863 0.835 0.823 ...
$ rrn : num 0.789 0.702 0.894 0.895 0.923 ...
$ asym2: num 0.177 0.304 0.108 0.187 0.274 ...
$ asym3: num 0.0755 0.0975 0.0818 0.0651 0.13 ...
> str(rownames(op))
chr
2010 Aug 08
3
Does anybody know how to control the appearance of the end of the line in lattice?
Hi All,
I am plotting vertical lines using xyplot in lattice and type="h".
It works well, but the problem is that the tops of the lines are convex and the bottoms are concave.
Is there a way to flatten the tops and bottoms?
Here's my code:
Source<-matrix(1:30,10,3)
colnames(Source)<-c("x","y1","y2")
Source<-data.frame(Source)
xyplot(y2+y1~x,
2010 Sep 24
3
boundary check
Dear R,
I have a covariates matrix with 10 observations, e.g.
> X <- matrix(rnorm(50), 10, 5)
> X
[,1] [,2] [,3] [,4] [,5]
[1,] 0.24857135 0.30880745 -1.44118657 1.10229027 1.0526010
[2,] 1.24316806 0.36275370 -0.40096866 -0.24387888 -1.5324384
[3,] -0.33504014 0.42996246 0.03902479 -0.84778875 -2.4754644
[4,] 0.06710229 1.01950917
2003 Jul 13
3
How robust is mle in R?
A newbie question: I'm trying to decide whether to run a maximum likelihood
estimation in R or Stata and am wondering if the R mle routine is reasonably
robust. I'm fairly certain that, with this data, in Stata I would get a lot
of complaints about non-concave functions and unproductive steps attempted,
but would eventually have a successful ML estimate. I believe that, with
the
2009 Mar 23
4
newton method
Hi R-users,
Does R has a topic on newton's method?
Thank you for the info.
2009 Dec 06
1
R + Hull-White model using nonlinear least squares
Hi guys
I have data that contains the variances vt of the yields of 1, 2, 3, 4,
5,10, 20 year bonds. Assuming the Hull-White model for the yield of a t-year
zero-coupon bond, I have to estimate the ? of the Hull-White model using
nonlinear least squares and give a 95% con?dence interval for each
parameter. Please can you guys tell how to find out ? using R. Any
suggestion regarding what functions
2011 Apr 16
1
Applying interpolation within a convex hull
Hi there,
I have been using the Tps function (within the Fields package) for a while
now to interpolate different sedimentary units. Due to the method of
formation of the units I know that at some edges the thickness of the unit
decreases to zero. I was wondering if there was someway to specify that the
interpolation only occurs within the convex hull of the data, outside of
which the the values
2013 Jan 28
1
Adding 95% contours around scatterplot points with ggplot2
Hi all,
I have been looking for means of add a contour around some points in a
scatterplot as a means of representing the center of density for of the
data. I'm imagining something like a 95% confidence estimate drawn around
the data.
So far I have found some code for drawing polygons around the data. These
look nice, but in some cases the polygons are strongly influenced by
outlying points.
2009 Mar 09
2
Chull function
Hi everyone,
Using a simulation, I have to find what are the probabilities that, in a square region, the convex hull is a triangle, using the "chull" function. However, I have a hard time with the chull function, i did not see many examples in which the chull function is used. I searched a long time on google, but I did not find nothing. So, if anyone can help,
Thanks!