Displaying 20 results from an estimated 1100 matches similar to: "Concave hull"
2010 Mar 30
6
Error "singular gradient matrix at initial parameter estimates" in nls
I am using nls to fit a non linear function to some data.
The non linear function is:
y= 1- exp(-(k0+k1*p1+ .... + kn*pn))
I have chosen algorithm "port", with lower boundary is 0 for all of the
ki parameters, and I have tried many start values for the parameters ki
(including generating them at random).
If I fit the non linear function to the same data using an external
2009 Sep 30
3
A point in a vector?
Dear list,
I have a strange requirement .... I have a vector, for example v<-
c(0,0,0,0,1,2,4,6,8,8,8,8). I have a value,for example x<- 4.8.
I would like to understand in which sub interval of v is x. In this case, v
would be in the sub interval [4,6] that is in the subinterval starting from
element j=7 to the element j+1=8.
Can we do that with an R command?
Regards
--
Corrado Topi
2009 Sep 01
3
Strange error returned or bug in gam in mgcv????
Dear friends,
what is this error message in gam???? I cannot understand what it means ....
is it a bug?
gam_bray_scot24_pc_0505<gam(bray~s(PC1,PC2,PC3,PC4,PC5,
PC1.1,PC2.1,PC3.1,PC4.1,PC5.1),data=dist_scot24_vector_with_climate)
Error in if (length(data) != vl) { :
missing value where TRUE/FALSE needed
Calls: gam ... smooth.construct -> smooth.construct.tp.smooth.spec -> array
In
2009 Sep 03
3
goodness of "prediction" using a model (lm, glm, gam, brt, regression tree .... )
Dear R-friends,
How do you test the goodness of prediction of a model, when you predict on a
set of data DIFFERENT from the training set?
I explain myself: you train your model M (e.g. glm,gam,regression tree, brt)
on a set of data A with a response variable Y. You then predict the value of
that same response variable Y on a different set of data B (e.g. predict.glm,
predict.gam and so on).
From THE R BOOK -> Warning: In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!
2010 Mar 30
3
From THE R BOOK -> Warning: In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!
Dear friends,
I am testing glm as at page 514/515 of THE R BOOK by M.Crawley, that is
on proportion data.
I use glm(y~x1+,family=binomial)
y is a proportion in (0,1), and x is a real number.
I get the error:
In eval(expr, envir, enclos) : non-integer #successes in a binomial glm!
But that is exactly what was suggested in the book, where there is no
mention of a similar warning. Where am I
2009 Feb 25
3
Using very large matrix
Dear friends,
I have to use a very large matrix. Something of the sort of
matrix(80000,80000,n) .... where n is something numeric of the sort 0.xxxxxx
I have not found a way of doing it. I keep getting the error
Error in matrix(nrow = 80000, ncol = 80000, 0.2) : too many elements specified
Any suggestions? I have searched the mailing list, but to no avail.
Best,
--
Corrado Topi
Global
2009 Sep 10
2
Negative AIC
Dear R list,
I just obtained a negative AIC for two models (-221.7E+4
and -230.2E+4). Is that normal?
Regards
--
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
2008 Dec 11
2
Principal Component Analysis - Selecting components? + right choice?
Dear R gurus,
I have some climatic data for a region of the world. They are monthly averages
1950 -2000 of precipitation (12 months), minimum temperature (12 months),
maximum temperature (12 months). I have scaled them to 2 km x 2km cells, and
I have around 75,000 cells.
I need to feed them into a statistical model as co-variates, to use them to
predict a response variable.
The climatic
2009 Aug 27
19
Best R text editors?
Quick informal poll: what is everyone's favorite text editor for working
with R? I'd like to hear from people who are using editors that have
some level of direct R interface (e.g. Tinn-R, Komodo+SciViews). Thanks!
--j
--
Jonathan A. Greenberg, PhD
Postdoctoral Scholar
Center for Spatial Technologies and Remote Sensing (CSTARS)
University of California, Davis
One Shields Avenue
The
2009 Aug 24
2
Formulas in gam function of mgcv package
Dear R-experts,
I have a question on the formulas used in the gam function of the mgcv
package.
I am trying to understand the relationships between:
y~s(x1)+s(x2)+s(x3)+s(x4)
and
y~s(x1,x2,x3,x4)
Does the latter contain the former? what about the smoothers of all
interaction terms?
I have (tried to) read the manual pages of gam, formula.gam, smooth.terms,
linear.functional.terms but
2009 Aug 24
2
Formulas in gam function of mgcv package
Dear R-experts,
I have a question on the formulas used in the gam function of the mgcv
package.
I am trying to understand the relationships between:
y~s(x1)+s(x2)+s(x3)+s(x4)
and
y~s(x1,x2,x3,x4)
Does the latter contain the former? what about the smoothers of all
interaction terms?
I have (tried to) read the manual pages of gam, formula.gam, smooth.terms,
linear.functional.terms but
2009 Oct 02
1
Fetch large sized file from SQL
Hi List,
Does any one know what package I need to use in order to fetch/get a large
sized dataframe from SQL? I have already used sqldf package which is good
for fetching large sized csv files.
Thanks
Alireza
[[alternative HTML version deleted]]
2010 Mar 23
1
S4: Multiple inheritance
Hi all,
Working with S4 object, I definine two class foo1 and foo2. I define '['
(resp. '[<-') for the two classes.
Then I define a third class foo3 that inherit from both foo1 and foo2.
Is there a way to make '[' (resp. '[<-') for foo3 inherit from '['
(resp. '[<-') for foo1 and foo2?
Thanks
Christophe
2009 Jan 17
2
Concave Hull
Dear Friends,
Here is an algorithm for finding concave hulls: http://get.dsi.uminho.pt/local/
Has anyone implemented such an algorithm in R?
RSiteSearch('concave hull') didn't reveal one (I think).
_____________________________
Professor Michael Kubovy
University of Virginia
Department of Psychology
Postal Address:
P.O.Box 400400, Charlottesville, VA 22904-4400
Express Parcels
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 Sep 29
4
Something wrong with my function Please Help
Hi R users,
I try to build a function to compute odds ratio and relative risk however
something wrong. I stuck for many hours but I really don't know how to solve
it. Would someone please give me a hint?
> OR.RR<-function(x){
+ x <- as.matrix(any(dim(x)==2))
+ OR<-(x[1,1]*x[2,2])/(x[1,2]*x[2,1])
+ RR<-(x[1,1]/(sum(x[1,])))/(x[2,1]/(sum(x[2,])))
+
2011 Apr 29
2
Summer student internship placement at University of York / YCCSA / SEI (paid)
Dear R-lings,
I did not know which list to post to, because it is a studentship so not
really a job, so it did not fit the r-sig-jobs list .... and it is about
devloping an extension package interfaced with R .... I hope I did not upset
anyone. If so apologies.
The Centre For Complex systems Analysis at the University of York (YCCSA) in
UK in collaboration with Stockholm Environment
2009 Dec 01
2
Distance between sets of points in transformed environmental space
Dear friends,
I have several sets of points in a transformed environmental space. Each set
of points can be represented as a cloud in the environmental space.
This space is spanned by n coordinates, corresponding to the first n PCs of 36
PCs of some environmental variables (12 monthly minimum temperatures, 12
monthly maximum temperature, 12 monthly precipitations).
I would like to calculate
2009 Sep 28
6
SAS user now converting to R - Help with Transpose
I am just starting to code in R and need some help as I am used to doing this
in SAS.
I have a dataset that looks like this:
Chemical Well1 Well2 Well3 Well4
BOD 13.2 14.2 15.5 14.2
O2 7.8 2.6 3.5 2.4
TURB 10.2 14.6 18.5 17.3
and so on with more chemicals....
I would like to transpose my data so that it looks like this:
Chemical WellID Value
BOD Well1 13.2
BOD Well2 14.2
BOD Well3 15.5
BOD
2011 May 03
1
Visiting Researcher, species distribution modelling, Cali, Colombia
Dear All,
The Decision and Policy Analysis (DAPA) program of the International Center
for Tropical
Agriculture (CIAT), a not-for-profit agriculture, biodiversity and
ecosystems research center,
supported by the Consultative Group of International Agricultural Research
(CGIAR), with
headquarters in Cali, Colombia is looking for a visiting researcher to work
on various modeling
projects, primarily