similar to: SUMMARY: "elementary sapply question"

I am discovering sapply! :-) Could you please help me with a very elementary question? Here is what I know. The following two programs generate the same answer. --------------------------------+---------------------------------------- Loops version | sapply version --------------------------------+----------------------------------------

Ajay, thank you very much for picking up that age-old habit of posting summaries. It existed years ago on s-help and I find it is still a great thing: I would not have bothered to read your original question nor the answers you got, but I did read the summary -- and I learned something quite interesting! Maybe some others who receive multiple non-elementary answers to their questions could

Folks, S_t = (x_t, y_t) is the state of a system at time t. There is an iterative function which converts S_t into S_{t+1}. I can easily write this in R like this: iterate <- function(S) { list(S$x+1, S$y+1) } So this function eats S_t and makes S_{t+1} and I can say S2 <- iterate(S1) My question: suppose I want to iterate from 1..10, what is the data structure

Suppose one has x <- c(1, 2, 7, 9, 14) y <- c(71, 72, 77) How would one write an R function which alternates between elements of one vector and the next? In other words, one wants z <- c(x[1], y[1], x[2], y[2], x[3], y[3], x[4], y[4], x[5], y[5]) I couldn't think of a clever and general way to write this. I am aware of gdata::interleave() but it deals

Folks, I asked a question on this mailing list about the subset support of lm(). In a flash, I got three helpful responses from Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net> Erin Hodgess <hodgess at gator.uhd.edu> and Peter Dalgaard <p.dalgaard at biostat.ku.dk> :-) and it was just great. The mistake I was making was in not understanding the notion of a

I have a program which is doing a few thousand runs of lm(). Suppose it is a simple model y = a + bx1 + cx2 + e I have the R object "d" where d <- summary(lm(y ~ x1 + x2)) I would like to obtain Var(x2) out of "d". How might I do it? I can, of course, always do sd(x2). But it would be much more convenient if I could snoop around the contents of summary.lm and

I have an elementary programming question. Could someone please point me in the right direction? I have a function which will run for thousands of companies. At each invocation, it returns 2 numbers. I plan to do something like: think_one_firm <- function(filename) { # Do stuff return(list(x=x,y=y)) } So for each of the firms in my dataset, I will call

I think I have isolated a problem with integration between Sweave and beamer. Could you please see the file: http://www.mayin.org/ajayshah/tmp/bugdemo.Rnw Unfortunately, it uses some of my internal libraries, so you can't run it. When I put it through Sweave, I get: http://www.mayin.org/ajayshah/tmp/bugdemo.tex which is, of course, a generic latex file which you can read and

I learned R & MLE in the last few days. It is great! I wrote up my explorations as http://www.mayin.org/ajayshah/KB/R/mle/mle.html I will be most happy if R gurus will look at this and comment on how it can be improved. I have a few specific questions: * Should one use optim() or should one use stats4::mle()? I felt that mle() wasn't adding much value compared with optim, and

Folks, I am using R 2.1.1 on Apple OS X 10.3. Earlier, I used to say $ sudo R > update.packages() and all the packages used to get installed. For several weeks, I noticed that nothing has been coming through. I used the R-for-Mac graphics console and I find that there are many packages where new versions have come out which I don't have. Is something wrong with update.packages()? I

I have two data frames. Suppose the first has rows r1 r2 r3 and the second has rows R1 R2 R3 I'd like to generate the data frame: r1 R1 r1 R2 r1 R3 r2 R1 r2 R2 r2 R3 r3 R1 r3 R2 r3 R3 How would I go about doing this? I'm sure there's a clean way to do it but I find myself thinking in loops. -- Ajay Shah

How do I parse a date "yyyymmdd"? I tried asking chron(s, "ymd") but that didn't work. Would the date parsing routines of the Date class of 1.9 grok this? -- Ajay Shah Consultant ajayshah at mayin.org Department of Economic Affairs http://www.mayin.org/ajayshah Ministry of Finance, New Delhi

I wondered was people on this list felt about this article: http://www.voxeu.org/index.php?q=node/2363 which talks about the problems of obtaining sound answers in numerical optimisation in settings such as MLE or NLS. -- Ajay Shah http://www.mayin.org/ajayshah ajayshah at mayin.org http://ajayshahblog.blogspot.com <*(:-? -

I have : raw <- read.table("monthly.text", skip=3, sep="|", col.names=c("junk", "junk2", "wpi", "g.wpi", "wpi.primary", "g.wpi.primary", "wpi.fuel", "g.wpi.fuel", "wpi.manuf", "g.wpi.manuf",

How does one convert objects c("a","b","c") and "d" into "abcd"? > paste(c("a","b","c"), "d") of course yields [1] "a d" "b d" "c d" -- Ajay Shah http://www.mayin.org/ajayshah ajayshah at mayin.org

Folks, I have a personal package which used to build fine. Today when I tried to build the package again, some errors popped up. Could you please help? When I paste the offending function into an R it works correctly. But the package build breaks. $ R CMD check ansecon * checking for working pdflatex ... OK * using log directory '/Users/ajayshah/L/R/packages/ansecon.Rcheck' * using R

Folks, I have a time-series of 875 readings of the weekly returns of a stock market index (India's Nifty). I am interested in the AR(1) coefficient. When I do arima(r, order=c(1,0,0)) I get a statistically significant AR1 coefficient. If we apply the ordinary bootstrap to this problem, this involves sampling with replacement, which destroys the time-series structure. Hence, if we do

Hi Ajay: A casual search of google using terms like "MCMC", "Markov Chains", "Monte Carlo", and "tutorial" pulled up over 4000 hits. A few links that may interest you, I thought, like: http://csep1.phy.ornl.gov/CSEP/MC/MC.html http://www.stat.fi/isi99/proceedings/arkisto/varasto/gree0167.pdf http://www.maths.soton.ac.uk/staff/Sahu/utrecht/ ... and so

See http://mayin.nfshost.com/ajayshah/KB/R/documents/mle/mle.html -- Ajay Shah http://www.mayin.org/ajayshah ajayshah at mayin.org http://ajayshahblog.blogspot.com <*(:-? - wizard who doesn't know the answer.

Folks, A nice new data resource has come up -- http://data.un.org/ I thought it would be wonderful to setup an R function like tseries::get.hist.quote() which would be able to pull in some or all of this data. I walked around a bit of it and I'm not able to map the resources to predictable URLs which can then be wget. There's some javascript going on that I'm not understanding.