Comments for Victor A. Barger

Comment on Pasting SPSS charts into iWork Pages by jaclyn

jaclyn — Wed, 07 Sep 2011 20:06:35 +0000

Thank you so much, This simple explanation helped out a ton!

Comment on Raising a matrix to a power in R by Shihai

Shihai — Wed, 27 Jul 2011 18:24:35 +0000

Thanks for sharing! I meet the same problem with R today.

Comment on Raising a matrix to a power in R by Daniel

Daniel — Sun, 15 May 2011 06:20:25 +0000

Thanks, Victor. That’s very helpful, especially for Markov chains. However, if you had to compute A^5 by hand, first you’d compute A^2, then square the result to get A^4 in two steps, and finally multiply by A once more. I’ve generalized this approach by adding an additional function that, for a nonnegative integer, returns an array of binary digits. This should involve about one half log base 2 of p matrix multiplications rather than p-1. Sorry by the way for the lack of comments — documentation is not my strong suit.

dec2bin = function(n){

p <- n

if(p==0) return(0)

bin.rep <- NULL

k 0){

q <- p%%2^k
bin.rep <- c(sign(q),bin.rep)
p <- p – q
k <- k+1

}

return(bin.rep)

}

eye = function(n){

return(diag(1,n,n))

}

mpower = function(M,p){

A <- as.matrix(M)

m <- dim(A)[1]
n <- dim(A)[2]

if(m != n) stop("Matrix must be square.")

if(p == -1) return(solve(A))

p <- dec2bin(p)

l <- length(p)

B <- eye(n)

for(k in l:1){

if(p[k]) B <- B%*%A
A <- A%*%A

}

return(B)

}

Comment on Proust was a Neuroscientist by Théodor Swann

Théodor Swann — Tue, 31 Aug 2010 10:00:41 +0000

This relationship is, particular, a familial one, because we know that his parents where too kynds of intelectuals.scientific (father) and artistic (mother). But in his book, the scientific instrument is used for a more material way of understanding, the subtil mechanism is achieved by sensibility, fact wich is described by Marcel Proust in a preface ( Jean Santeuil I suppose) as the ultimate intelectual apparatus wich leads human to understanding, namely truth.

Comment on Seamless integration of Papers and DEVONthink by Tim Norman

Tim Norman — Tue, 21 Jul 2009 15:57:50 +0000

Great tip – just out of interest does this use more filespace or less than importing the PDF’s into Devonthink?

Also just wondered whether you might have any ideas about something I’m trying to do:

I’m using Devonthink as well & just wondered whether you might have found a good way of searching for Bible references in your Devonthink database.

E.g. I want to find a talk or some notes on John 6:51-18, but I don’t want to find all the docs with just the word ‘John’ in it, and docs on John 6 might be useful, as might docs on John 5-8

Any ideas?

Thanks

Tim

Comment on The Really Hard Science by NSF concludes “science hard” « Victor Barger

NSF concludes “science hard” « Victor Barger — Mon, 20 Apr 2009 03:53:13 +0000

[...] 19, 2009 by Victor From The Onion, a bit of humor related to my previous post: INDIANAPOLIS—The National Science Foundation’s annual symposium concluded Monday, with the [...]

Comment on Raising a matrix to a power in R by Jasja Dekker

Jasja Dekker — Sun, 19 Apr 2009 20:20:52 +0000

Very nice, thanks for sharing this very effective bit of code. It is strange that this was never added to the base of R.

Comment on What They Didn't Teach You in Graduate School by Academic Career Links

Academic Career Links — Fri, 27 Mar 2009 17:31:17 +0000

More related material including a series of four papers by the same authors can be found here.

Comment on Raising a matrix to a power in R by Tudor

Tudor — Thu, 12 Mar 2009 15:56:27 +0000

Great, thanks for this. What about defining mpower for negative exponents, e.g.

mpower(M,-p^2)= solve(mpower(M,p^2))

Comment on Raising a matrix to a power in R by Andrew

Andrew — Sat, 29 Nov 2008 22:47:22 +0000

I have been lost on this one for a few months and hadn’t come up with a simple solution. This isn’t complete but it’s excellent for my purposes. Thank you!