Re: [R] OT: any recommendation for scripting language
On 12/23/06, Wensui Liu [EMAIL PROTECTED] wrote: from statisticians' point of view, which scripting language is worth to learn, perl, python, or any other recommendation? (Most likely, I will be learning it in windows.) Since I am not in research, I will prefer one widely used in industry and related to statistical work. It seems R would be the language of choice if you require related to statistical work. I would be surprised if any general scripting language would restrict themselves to statistics. if you recommend one, I will really appreciate it if you could point out a good source for learning as well. I find Ruby to be the closest language to the way I think about programming. It's fully object oriented, dynamically typed, open-source, free, and runs on just about any platform. Sophisticated IDE's are available and it can also run easily from the command line (like Perl). Ruby is fun to use. There are a lot of online Ruby resources and also printed material. Here are just a few. Language overview: http://en.wikipedia.org/wiki/Ruby_%28programming_language%29 Main Website: http://www.ruby-lang.org/en/ Learning Ruby: http://pine.fm/LearnToProgram/ http://www.math.umd.edu/~dcarrera/ruby/0.3/index.html http://poignantguide.net/ruby/ Give it a try online: http://tryruby.hobix.com/ Book: http://www.rubycentral.com/book/ [NB: This free online book is for Ruby 1.6. Another printed and PDF book is available for Ruby 1.8] http://pragmaticprogrammer.com/titles/ruby/index.html Newsgroup: http://groups.google.com/group/comp.lang.ruby thank you so much! Your welcome! Have a happy holiday. Thank you, I am. 8-) I hope everyone is having a nice holiday. Richard Graham __ R-help@stat.math.ethz.ch 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.
Re: [R] Matrix-vector multiplication without loops
On 11/14/06, Ravi Varadhan [EMAIL PROTECTED] wrote:
I am trying to do the following computation:
p - rep(0, n)
coef - runif(K+1)
U - matrix(runif(n*(2*K+1)), n, 2*K+1)
for (i in 0:K){
for (j in 0:K){
p - p + coef[i+1]* coef[j+1] * U[,i+j+1]
} }
I would appreciate any suggestions on how to perform this computation
efficiently without the for loops?
This kicks butt on my machine:
p - as.vector(U %*% convolve(coef,rev(coef),type=open))
HTH!
Richard Graham
JHU '84 EECS
__
R-help@stat.math.ethz.ch 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.
Re: [R] Dataset on Baltimore home energy costs
elect: Total cost of electricity (including delivery and commodity charges) With Maryland's BGE/PSC/State Legislature rate control, does anybody _really_ know what the total cost is? That may be what you paid then, but was that the total cost? The cost data may be difficult to compare with non rate controlled utility cost data. Richard Graham __ R-help@stat.math.ethz.ch 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.
Re: [R] Error Correcting Codes, Simplex
On 10/16/06, Björn Egert [EMAIL PROTECTED] wrote: On 10/8/06, Egert, Bjoern [EMAIL PROTECTED] wrote: Hello, Is there a way in R to construct an (error correcting) binary code e.g. for an source alphabet containing integers from 1 to say 255 with the property that each pair of distinct codewords of length m is at Hamming distance exactly m/2 ? I was suggested to use so called simplex codes, which should be fairly standard, but I haven't found a direct way via R packages to do so, that's why I ask whether there might be in indirect way to solve this problem. Example: v1 =c(1,2,3,4) v2 =c(1,2,5,6) similarity(v1,v2)=0.5, (because 2 out of 4 elements are equal). Obviously, a binary representation of would yield a different similarity of: binary(v1) =001 010 011 100 binary(v1) =001 010 101 110 similarity(binary(v1),binary(v2))= 9/12 Remark: The focus here is not on error correction, but rather the binary encoding retaining similarity of the elements of vectors. Many thanks, Bjoern Bjoern, NB: I'm an R newbie and I only know a bit about error correcting codes. I haven't seen any responses to your questions and I don't know if you still have a need, but it is certainly possible to construct forward error correction codes with all the great math capability in R. It seems you want to generate code words that still have the original bits present. These are systematic codes and there are lots of them available to use. Many codes are specified by the code word length (n), number of original data bits in each code word (k), and the minimum Hamming distance of the code words (d) as a [n,k,d] code. Simplex Codes have these parameters: [2^k - 1, k, 2^(k - 1)]. These codes could be generated as a simple matrix multiply in R, but are you sure that's what you want? The code words will be quite long. Regards, Richard Graham Hello, thank you. yes, basically, that's what I want. Just a binary encoding of an arbitrary integer value (or vector of integers) with the property that each pair of distinct integer values have an equal Hamming- distance (m/2), so as to be able to a similarity search I got the idea from: Gionis: Efficient and Tunable Similar Set Retrieval (Chap 3.2) regards Bjoern Bjoern, I read only the section of the paper you mention and I'll trust that the stated properties of Simplex Codes are true. I haven't researched or verified it. [from http://magma.maths.usyd.edu.au/] Magma is a large, well-supported software package designed to solve computationally hard problems in algebra, number theory, geometry and combinatorics. It provides a mathematically rigorous environment for computing with algebraic, number-theoretic, combinatoric and geometric objects. I don't understand a fraction of its capability but I still find it to be very useful. In fact, they have an online calculator that will give you the generator matrix you want. The online Magma calculator is at: http://magma.maths.usyd.edu.au/calc/ To calculate the generator matrix I think you are asking for, go to the above URL and cut/paste the following command: ExtendCode(SimplexCode(8)); Click Evaluate and the output window will contain a [256, 8, 128] Linear Code over GF(2). You'll need to massage this a bit to use it as a matrix for R. I'd use Ruby to do this, but anything will do. If you want to encode more/less than 8 bits, you can modify the above argument to SimplexCode. I used ExtendCode so that the codeword length == Dmin * 2 The Gionis claim I'll research or verify sometime is that _every_ pair of Simplex Code words of length m have Hamming distance == m/2. If you have a reference to a proof, I'd like to read it (like I said, I only know a bit about ECC). Good Luck with your work! Richard Graham __ R-help@stat.math.ethz.ch 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.
Re: [R] Error Correcting Codes, Simplex
On 10/8/06, Egert, Bjoern [EMAIL PROTECTED] wrote: Hello, Is there a way in R to construct an (error correcting) binary code e.g. for an source alphabet containing integers from 1 to say 255 with the property that each pair of distinct codewords of length m is at Hamming distance exactly m/2 ? I was suggested to use so called simplex codes, which should be fairly standard, but I haven't found a direct way via R packages to do so, that's why I ask whether there might be in indirect way to solve this problem. Example: v1 =c(1,2,3,4) v2 =c(1,2,5,6) similarity(v1,v2)=0.5, (because 2 out of 4 elements are equal). Obviously, a binary representation of would yield a different similarity of: binary(v1) =001 010 011 100 binary(v1) =001 010 101 110 similarity(binary(v1),binary(v2))= 9/12 Remark: The focus here is not on error correction, but rather the binary encoding retaining similarity of the elements of vectors. Many thanks, Bjoern Bjoern, NB: I'm an R newbie and I only know a bit about error correcting codes. I haven't seen any responses to your questions and I don't know if you still have a need, but it is certainly possible to construct forward error correction codes with all the great math capability in R. It seems you want to generate code words that still have the original bits present. These are systematic codes and there are lots of them available to use. Many codes are specified by the code word length (n), number of original data bits in each code word (k), and the minimum Hamming distance of the code words (d) as a [n,k,d] code. Simplex Codes have these parameters: [2^k - 1, k, 2^(k - 1)]. These codes could be generated as a simple matrix multiply in R, but are you sure that's what you want? The code words will be quite long. Regards, Richard Graham __ R-help@stat.math.ethz.ch 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.
