Displaying 20 results from an estimated 72 matches for "convex".

Did you mean:
convey

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...

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
-.-.-.-....

2007 Mar 26

1

sampling from the uniform distribution over a convex hull

Ranjan Maitra writes:
> Does anyone have a suggestion (or better still) code for sampling
> from the uniform distribution over the convex hull of a set of
> points?
This is implemented in library 'spatstat'.
If x and y are vectors of coordinates of your initial set of points,
library(spatstat)
W <- convexhull.xy(x, y)
P <- runifpoint(42, W)
will compute the convex hull and generate 42 independent
u...

2014 Oct 12

1

Is xyz point inside 3d convex hull?

Hi everyone,
I wonder if there is a code in r that can generate a 3d convex hull from a data-frame containing 3 columns and then use another database with the same three columns and for each row determine if the xyz point is inside or not the convex hull generated with the first database?
The package geometry allows to calculate a hull and it's volume. I was planning...

2017 Nov 21

0

[R-pkgs] CVXR: Convex Programming in R

Dear R Users,
We are pleased to announce the first release of CVXR which implements
Disciplined Convex Programming (DCP) in R on CRAN. Like CVXPY in Python,
CVXR provides a domain specific language for formulating
convexoptimization problems in a natural way following mathematical
convention and DCP rules. The system analyzes the problem, verifies its
convexity, converts it into a canonical form...

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...

2005 Sep 01

1

convex-polygon in scatter plot

Hello,
I am trying to draw a convex-polygon (envelope) connecting the outer points
(of a particular class) in a scatter plot
[which I want to do to illustrate the range of a particular type of samples
in an ordination plot].
Is there any function to plot this kind of polygon?
Kind regards
Zlatko Petrin

2006 May 12

1

[ESRI-L] outline polygons of point clumps

Sorry, I did not make my question clear. Since I have a point theme
with many points, some of them may clump together. the problems here
are:
1. how to find clumps in a point theme?
2. the convex-hull extension I found only deal with all the points in
a theme at each time? how to make each convex hull around each point
clump automatically?
Thanks.
Xiaohua
On 5/12/06, Bob Booth <bbooth at esri.com> wrote:
> Xiaohua,
>
> That would be one way to do it. There are o...

2009 Feb 18

1

alpha shape function

Hi all,
I want to approximate te shape of an area defined by a set of points.
The convex hull is not good enough, but I think that an alpha shape
would be fine. I did an RSiteSearch(), google search, RSeek.org search,
looked at the CRAN Views, but was unable do find a function in R that
computes the alpha shape. Does anyone know if there is such a function
in R?
Theank you very much...

2017 Oct 20

0

What exactly is an dgCMatrix-class. There are so many attributes.

Subsetting using [] vs. head(), gives different results.
R code:
> head(train$data, 5)
[1] 0 0 1 0 0
> train$data[1:5, 1:5]
5 x 5 sparse Matrix of class "dgCMatrix"
cap-shape=bell cap-shape=conical cap-shape=convex
[1,] . . 1
[2,] . . 1
[3,] 1 . .
[4,] . . 1
[5,] . . 1
cap-shape=flat cap-...

2013 Apr 16

1

update config.guess and config.sub to support aarch64

Hello,
would it be possible to update config.sub and config.guess to the latest versions (or at least version
from automake-1.13.1) in order to support new architectures based on the ARM 64 bit CPU?
Patch: http://plautrba.fedorapeople.org/openssh/openssh-latest-config.sub-config.guess.patch
Related Fedora bug: https://bugzilla.redhat.com/show_bug.cgi?id=926284

2017 Oct 20

4

What exactly is an dgCMatrix-class. There are so many attributes.

...1 24 28 32 ...
> ..@ p : int [1:127] 0 369 372 3306 5845 6489 6513 8380 8384 10991
> ...
> ..@ Dim : int [1:2] 6513 126
> ..@ Dimnames:List of 2
> .. ..$ : NULL
> .. ..$ : chr [1:126] "cap-shape=bell" "cap-shape=conical"
> "cap-shape=convex" "cap-shape=flat" ...
> ..@ x : num [1:143286] 1 1 1 1 1 1 1 1 1 1 ...
> ..@ factors : list()
>
> > Where is the data, is it in $p, $i, or $x?
>
> So the "data" (meaning the values of the sparse matrix) are in the @x
> leaf. The values all...

2004 Jun 01

0

qhull in R?

Hi,
does anyone know if there is an implementation
of qhull (http://www.qhull.org/) in R? anyone is
planning on it?
"Qhull computes convex hulls, Delaunay triangulations, halfspace
intersections about a point, Voronoi diagrams, furthest-site Delaunay
triangulations, and furthest-site Voronoi diagrams. It runs in 2-d, 3-d,
4-d, and higher dimensions. It implements the Quickhull algorithm for
computing the convex hull. Qhull handles...

2012 Mar 07

0

sparsenet: a new package for sparse model selection

We have put a new package sparsenet on CRAN.
Sparsenet fits regularization paths for sparse model selection via coordinate descent,
using a penalized least-squares framework and a non-convex penalty.
The package is based on our JASA paper
Rahul Mazumder, Jerome Friedman and Trevor Hastie: SparseNet : Coordinate Descent with Non-Convex Penalties. (JASA 2011)
http://www.stanford.edu/~hastie/Papers/Sparsenet/jasa_MFH_final.pdf
We use Zhang's MC+ penalty to i...

2012 Mar 07

0

sparsenet: a new package for sparse model selection

We have put a new package sparsenet on CRAN.
Sparsenet fits regularization paths for sparse model selection via coordinate descent,
using a penalized least-squares framework and a non-convex penalty.
The package is based on our JASA paper
Rahul Mazumder, Jerome Friedman and Trevor Hastie: SparseNet : Coordinate Descent with Non-Convex Penalties. (JASA 2011)
http://www.stanford.edu/~hastie/Papers/Sparsenet/jasa_MFH_final.pdf
We use Zhang's MC+ penalty to i...

2017 Oct 20

3

What exactly is an dgCMatrix-class. There are so many attributes.

Dear R list,
I came across dgCMatrix. I believe this class is associated with sparse
matrix.
I see there are 8 attributes to train$data, I am confused why are there so
many, some are vectors, what do they do?
Here's the R code:
library(xgboost)
data(agaricus.train, package='xgboost')
data(agaricus.test, package='xgboost')
train <- agaricus.train
test <- agaricus.test

2017 Oct 20

0

What exactly is an dgCMatrix-class. There are so many attributes.

...: int [1:143286] 2 6 8 11 18 20 21 24 28 32 ...
..@ p : int [1:127] 0 369 372 3306 5845 6489 6513 8380 8384 10991 ...
..@ Dim : int [1:2] 6513 126
..@ Dimnames:List of 2
.. ..$ : NULL
.. ..$ : chr [1:126] "cap-shape=bell" "cap-shape=conical" "cap-shape=convex" "cap-shape=flat" ...
..@ x : num [1:143286] 1 1 1 1 1 1 1 1 1 1 ...
..@ factors : list()
> Where is the data, is it in $p, $i, or $x?
So the "data" (meaning the values of the sparse matrix) are in the @x leaf. The values all appear to be the number 1. The @i...

2006 Apr 26

1

Polygon-like interactive selection of plotted points

[Please CC me for all replies, since I am not currently subscribed to
the list.]
Hi all,
I have the following problem/question: Imagine you have a two-
dimensional plot, and you want to select a number of points, around
which you could draw a polygon. The points of the polygon are defined
by clicking in the graphics window (locator()/identify()), all points
inside the polygon

2013 Mar 05

2

Questions on implementing logistic regression

Hi there,
I am trying to write a tool which involves implementing logistic
regression. With the batch gradient descent method, the convergence is
guaranteed as it is a convex problem. However, I find that with the
stochastic gradient decent method, it typically converges to some random
points (i.e., not very close to the minimum point resulted from the batch
method). I have tried different ways of decreasing the learning rate, and
different starting points of weights. H...