search for: welch

...o, in pseudo R+perl notation is f <- function(a,b) list(a+b,a-b) (c,d) <- f(1,2) and have c be assigned 1+2 and d be assigned 1-2. right now, I use the clunky x <- f(1,2) c <- x[[1]] d <- x[[2]] rm(x) which seems awful. is there a nicer syntax? regards, /iaw ---- Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)

dear r experts---Is there a multicore equivalent of by(), just like mclapply() is the multicore equivalent of lapply()? if not, is there a fast way to convert a data.table into a list based on a column that lapply and mclapply can consume? advice appreciated...as always. regards, /iaw ---- Ivo Welch (ivo.welch at gmail.com)

Hello Using R 2.2.1 on a Windows machine. Has anyone programmed the Welch test for equality of variances? I tried RSiteSearch, but this gave references to t test and oneway.test, which are not quite what I need.....I need the Welch test itself, for use in a meta-analysis (to determine if variances are equal). TIA Peter Peter L. Flom, PhD Assistant Director, Statis...

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This is not a bug report but didn't see another way to ask a question. For the approximate t-test assuming unequal variances, the R docs cite Welch's method for the df of the approximating distribution. I have several methods books, and they all uses Satterthwaite's method. Why does R use Welch's method where can I learn about Welch's method? Sincerely, David Allen -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-....

..., I can compute (X' X)^(-1) s^2 myself. Has someone written a fast se() function? incidentally, I think this would make a nice addition to the R base. I presume it is not uncommon for a statistician also to want to use the se of coef estimates. pointers appreciated. regards, /iaw ---- Ivo Welch (ivo.welch@brown.edu, ivo.welch@gmail.com) [[alternative HTML version deleted]]

is it possible to throw a stop() that is so hard that it will escape even tryCatch? /iaw ---- Ivo Welch (ivo.welch at gmail.com)

...any millions of observations, a few thousand variables (most of these variables are interaction fixed effects). could someone please point me to packages, if any, that would help me estimate such models? (can these problems be split over many different cores?) advice appreciated. /iaw ---- Ivo Welch (ivo.welch@brown.edu, ivo.welch@gmail.com) CV Starr Professor of Economics (Finance), Brown University http://welch.econ.brown.edu/ [[alternative HTML version deleted]]

...nd another categorization for importance (e.g., like "common" for lm and "obscure" for ..). Such categorizations require intelligence. if I am going to do this for myself, I think a csv spreadsheet may be a good idea to make it easy to resort by keys. regards, /iaw ---- Ivo Welch (ivo.welch@gmail.com) [[alternative HTML version deleted]]

...iables). Let's presume one of the y variables contains only NA's. I believe I now cannot use lm(y ~ X), because one of the regressions will throw the lm.fit exception. (all the other y vectors should have worked.) or is there a way to get lm() to work in such situations? /iaw ---- Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)

dear r community... it loks like i won't be able to reach homogenity of variance for my dataset, so i end up with welch anova instead of regular anova. documentation on this test is rather scarce, so maybe someone here can enlighten me a bit: - do i understand that no two-way implementation of the welch anova has been developed yet? - is there a post-hoc test for welch anovas implemented in R? thanks a lot, lukas...

...real and user, using the unix timing function). "do-onecore" takes about 300 seconds. "do-multicore" takes about 210 seconds real, (300 seconds user). this seems pretty disappointing. the cores are not used for the most part, either. feedback appreciated. /iaw ---- Ivo Welch (ivo.welch at gmail.com)

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...$`A` [1] 2 3 $`B` [2] 4 5 then the revised by() would instead produce charid ?m ?s A ? ? ? ? ?2 ?3 B ? ? ? ? ?4 ?5 working with data frames is often more intuitive than working with the output of by(). the R wizards are probably chuckling now about how easy this is... regards, /iaw ---- Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)

...m=c(0,5), type="n") text(1,1, "&spades;") text(2,2, "&hearts;") text(3,3, "&diams;") text(4,4, "&clubs;") dev.off() (these are the characters that I need the most NOW, but this is a more generic question.) sincerely, /iaw ---- Ivo Welch (ivo.welch at gmail.com)

dear R experts---is there a function that prints a data frame to a string? cat() cannot handle lists, so I cannot write cat("your data frame is:\n", df, "\n"). regards, /iaw ---- Ivo Welch (ivo.welch@gmail.com) [[alternative HTML version deleted]]

...r ago, and then the answer was no. for those who are googling the group for the answer to this question, in the meantime, the poor man's version of "by" is mclapply( split( ds, factor ), FUN ) I don't know the poor man's version of "ave". sincerely, /iaw ---- Ivo Welch (ivo.welch at gmail.com) http://www.ivo-welch.info/

...nkle "cat" statements everywhere, just to locate the line where the error appears.) Of course, I would really love to see the line in my program that triggered this, but I have asked this before, and I understand this is too difficult to get into the R language. regards, /iaw ---- Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)

...re what packages are actually imported. ?importIntoEnv tells me that it is not intended to be used. how can another program declare exactly what functions it wants to import? (frankly, I would love to turn all default autovivification off in my program, but that's not possible.) /iaw ---- Ivo Welch (ivo.welch at gmail.com)

...Oct 2002 roxburg@kih.net wrote: >> This is not a bug report but didn't see another way to >> ask a question. TL> Well, you could try the r-help or r-devel mailing lists >> For the approximate t-test assuming unequal variances, >> the R docs cite Welch's method for the df of the >> approximating distribution. I have several methods >> books, and they all uses Satterthwaite's method. Why >> does R use Welch's method where can I learn about Welch's >> method? >> TL> It'...