search for: xiaohua

...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 others. > Try searching ArcScripts for "convex hull" > http://arcscripts.esri.com/ > > For example: > http://arcscripts.esri.com/details.asp?dbid=145...

Hi All, Does anyone know how to compare the means of several circular-data samplings? Any related websites, references and softwares? Thanks Xiaohua -- Xiaohua Dai, Dr. [[alternative HTML version deleted]]

Hi R users, Hope the question is not too simple: How to use a for loop to generate two lists as below: testlist <- list(test1, test2, ..., test1000) stringlist <- list("test1","test2",...,"test1000") Thanks Xiaohua

Hi R-profs, Maybe my question is a little off topic. Could any one tell me how to calculate a linear-circular correlation coefficient and its p-values? I had a quick look at circular and CircStats packages and did not find the related function. Thanks for any kindly help. Xiaohua -- Xiaohua Dai, Dr. Centre for Systems Research, Durban Institute of Technology P.O.Box 953, Durban 4000, South Africa Tel: +27-31-2042737(O) Fax: +27-31-2042736(O) Mobile: +27-723682954 Publications: http://www.getcited.org/?MBR=11061629

..."NT 5.1" version nodename "(build 2600) Service Pack 2" "DIT-SYSRESEARCH" machine login "x86" "xiaohuadai" user "xiaohuadai" > R.Version() $platform [1] "i386-pc-mingw32" $arch [1] "i386" $os [1] "mingw32" $system [1] "i386, mingw32" $status [1] "" $major [1] "2" $minor [1]...

Hi R users, Sorry for a simple question: I found different people use different i in set.seed(i), are there any rules to choose an i or one can choose as he likes? Thanks Xiaohua

Hi Gurus! I have a job that is to get randomly samples from point-based GIS data (sp called shape GIS files) under the total sum resctricted. For example, I would like to take random smaples under the 1000 persons in each city. The randomly sampled persons should not be over 1000 any case. Thank you in advance, -- Kum-Hoe Hwang, Ph.D. Phone : 82-31-250-3283 Email : phdhwang@gmail.com

Is there any routine to generate for one vector matrix. If I have X I want to generate start from zero to maximum value each vector. For example, I have a vector x = (4,2,3,1,4) I want to generate n=6 times, for 4, start 0 to 4, then 2 start 0 to 2, ect. The result something like this: generate(x,n=6) 1,1,2,1,4 1,2,3,0,3 4,0,1,1,1 3,1,0,1,4 0,0,3,0,0 4,1,3,0,4 Could anyone help me. Thanks.

...: 8 > neigh[1] [[1]] [1] 2 5 6 7 10 21 22 25 Is there way to index each element of neigh[1], i.e., the first is 2, the second is 5, ... ? Could you also give me an example of the function "queencell(rowcol, nrow, ncol, torus=FALSE, rmin=1, cmin=1)"? What's a rowcol? Thanks, Xiaohua -- Xiaohua Dai, Dr. Centre for Systems Research, Durban Institute of Technology P.O.Box 953, Durban 4000, South Africa [[alternative HTML version deleted]]

...minutes!! Are there any other tips to speed up R program? Or someone could indicate me some documents or websites on R code optimization? #OS: Win XP, CPU: Pentium IV, 3.20G, Memory: 1G #for() loop: 1000*1616*3*41, 3 data.frames (dim = c(1616,5), c(1616), c(1616) respectively) Thanks in advance, Xiaohua -- Xiaohua Dai, Dr. -------------------------------------------------------------------------------- * Postdoctoral in elephant-tree ecosystem simulation --------------------------------------------------------------------------------- Centre for Systems Research, Durban Institute of Technology P....

Hi R users, I use plot.circular(rad, stack=T,bins=4) and could just obtain the four stacks in the directions of 45, 135, 225 and 315 degrees. But I want them in 0, 90, 180 and 270 degrees. Is there any parameter or any other function to make it? Thanks for helping a R beginner. -- Xiaohua Dai, Dr. -------------------------------------------------------------------------------- Centre for Systems Research, Durban Institute of Technology P.O.Box 953, Durban 4000, South Africa Tel: +27-31-2042737(O) Fax: +27-31-2042736(O) Mobile: +27-723682954 Publications: http://www.getcited.org/?MBR...

This is slightly off-topic but I would be interested in whether anyone has succeeded in creating a filter expression for Google's gmail system that will select messages sent through the R-help and R-devel lists. It seems as if it should be easy to select on '[R]' or '[Rd]' in the subject line but I haven't been able to work out the exact syntax that would do this and not

...mple. In a IF ... ELSE ... statement "if(cond) cons.expr else alt.expr", IF and ELSE should be at the same line? For example, if (x1==12) { y1 <- 5 }else { y1 <- 3 } is right, while if (x1==12) { y1 <- 5 } else # Error: syntax error { y1 <- 3 } is wrong? Thanks -- Xiaohua Dai -------------------------------------------------------------------------------- Centre for Systems Research, Durban Institute of Technology P.O.Box 953, Durban 4000, South Africa Tel: +27-31-2042737(O) Fax: +27-31-2042736(O) Mobile: +27-723682954 [[alternative HTML version deleted]]

Hi R list: How can I "repeat" a data frame n times (with n>1000), and obtain a new data frame where all the n data frames are binded by rows? Thank you for your help Kenneth -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

...st had a quick look at the package adehabitat and did not find the function. To my knowledge, I could do it as follows: 1) make a grid map of my study area with cell values = 0; 2) assign 1 to the cells containing at least one point; 3) convert the 1-value cells into polygons. Am I right? Thanks Xiaohua

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Dear R helpers, I have a largish matrix (1300 x 1300) and I wish to find the row and column numbers that identify particular elements whose values I know in advance (for example, the row and column numbers for the maximum value of the matrix). I have looked in the help manual and found the functions 'row' and 'col' for finding the indices of a matrix. But, I can't figure out

I have the following code and I am not sure what's wrong or how to make it work. B <- matrix(1,nrow=50,ncol=2) for (i in 1:length(size.out)){ # length(size.out=2) these are the two variables X <- var.range[i,1] # min Y <- var.range[i,1] # min ratio <- size.out[,i] for (j in 1:groups)

Hello, is there a package in R that would allow map drawing: coastlines, country/state boundaries, maybe topography, rivers etc? Thanks for any guidance, Mark

Hi, I was playing with Mandelbrot sets and come up with the following code, I thought I would share: library(fields) # for tim.colors library(caTools) # for write.gif m = 400 # grid size C = complex( real=rep(seq(-1.8,0.6, length.out=m), each=m ), imag=rep(seq(-1.2,1.2, length.out=m), m ) ) C = matrix(C,m,m) Z = 0 X = array(0, c(m,m,20)) for (k in 1:20) { Z =