Re: [R] Poisson Regression: questions about tests of assumptions

2012-10-14 Thread Achim Zeileis
On Sun, 14 Oct 2012, Eiko Fried wrote: Thank you for the detailed answer, that was really helpful. I did some excessive reading and calculating in the last hours since your reply, and have a few (hopefully much more informed) follow up questions. 1) In the vignette("countreg", package = "pscl

Re: [R] Poisson Regression: questions about tests of assumptions

2012-10-14 Thread Wensui Liu
just a side note for your 4th question. for a small sample, clarke test instead of vuong test might be more appropriate and the calculation is so simple that even excel can handle it :-) On Sun, Oct 14, 2012 at 12:00 PM, Eiko Fried wrote: > I would like to test in R what regression fits my data

Re: [R] Poisson Regression: questions about tests of assumptions

2012-10-14 Thread Joshua Wiley
Hi Eiko, This is not a direct response to your question, but I thought you might find these pages helpful: On negative binomial: http://www.ats.ucla.edu/stat/R/dae/nbreg.htm and zero inflated poisson: http://www.ats.ucla.edu/stat/R/dae/zipoisson.htm In general this page lists a variety of dif

Re: [R] Poisson Regression: questions about tests of assumptions

2012-10-14 Thread Eiko Fried
Thank you for the detailed answer, that was really helpful. I did some excessive reading and calculating in the last hours since your reply, and have a few (hopefully much more informed) follow up questions. 1) In the vignette("countreg", package = "pscl"), LLH, AIC and BIC values are listed for

Re: [R] Poisson Regression: questions about tests of assumptions

2012-10-14 Thread Achim Zeileis
On Sun, 14 Oct 2012, Eiko Fried wrote: I would like to test in R what regression fits my data best. My dependent variable is a count, and has a lot of zeros. And I would need some help to determine what model and family to use (poisson or quasipoisson, or zero-inflated poisson regression), and

Re: [R] Poisson Regression

2011-03-30 Thread Ben Bolker
Jim Silverton gmail.com> writes: > > Is there R code that can do a Poisson Regression and plot the density of the > fitted values? > ?glm glm(...,family=poisson) ?predict.glm __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listi

Re: [R] Poisson Regression

2011-03-30 Thread Jim Silverton
Is there R code that can do a Poisson Regression and plot the density of the fitted values? -- Thanks, Jim. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read t

Re: [R] poisson regression

2010-11-10 Thread Mitchell Maltenfort
The other possibilities are: (1) you're missing a necessary interaction term (2) one of the variables affecting output just isn't in your data set. (3) you need to transform 'hosp_days' or 'age' -- are those the only two continuous variables? Might be worth trying to plot 'em versus # of hospital

Re: [R] Poisson Regression

2010-10-16 Thread Peter Dalgaard
On 10/14/2010 06:42 PM, Viechtbauer Wolfgang (STAT) wrote: > Since the number of parameters then rises linearly with the number of > subjects, this may be a case where maximum likelihood theory breaks > down, that is, a Neyman-Scott problem. My thought too. The basic structure is close to the Rasc

Re: [R] Poisson Regression

2010-10-14 Thread Viechtbauer Wolfgang (STAT)
ael Friendly Sent: Thursday, October 14, 2010 14:56 To: Antonio Paredes Cc: r-help@r-project.org Subject: Re: [R] Poisson Regression > On 10/13/2010 4:50 PM, Antonio Paredes wrote: >> Hello everyone, >> >> I wanted to ask if there is an R-package to fit the following >> Pois

Re: [R] Poisson Regression

2010-10-14 Thread Michael Friendly
On 10/13/2010 4:50 PM, Antonio Paredes wrote: Hello everyone, I wanted to ask if there is an R-package to fit the following Poisson regression model log(\lambda_{ijk}) = \phi_{i} + \alpha_{j} + \beta_{k} i=1,\cdots,N (subjects) j=0,1 (two levels) k=0,1 (two levels) treating the \phi_{i} as nui

Re: [R] Poisson Regression

2010-10-13 Thread Charles C. Berry
On Wed, 13 Oct 2010, David Winsemius wrote: On Oct 13, 2010, at 4:50 PM, Antonio Paredes wrote: Hello everyone, I wanted to ask if there is an R-package to fit the following Poisson regression model log(\lambda_{ijk}) = \phi_{i} + \alpha_{j} + \beta_{k} i=1,\cdots,N (subjects) j=0,1 (two le

Re: [R] Poisson Regression

2010-10-13 Thread Bill.Venables
Thursday, 14 October 2010 10:22 AM To: Antonio Paredes Cc: r-help@r-project.org Subject: Re: [R] Poisson Regression On Oct 13, 2010, at 4:50 PM, Antonio Paredes wrote: > Hello everyone, > > I wanted to ask if there is an R-package to fit the following Poisson > regression model > &g

Re: [R] Poisson Regression

2010-10-13 Thread David Winsemius
On Oct 13, 2010, at 4:50 PM, Antonio Paredes wrote: Hello everyone, I wanted to ask if there is an R-package to fit the following Poisson regression model log(\lambda_{ijk}) = \phi_{i} + \alpha_{j} + \beta_{k} i=1,\cdots,N (subjects) j=0,1 (two levels) k=0,1 (two levels) treating the \phi_{i

Re: [R] Poisson regression: computation of linear combination of coefficients. Should one use the scaled var-cov matrix?

2010-01-29 Thread John Sorkin
Peter, I should have added that because I have over dispersion, I am ruining a quasipoisson regression. John John David Sorkin M.D., Ph.D. Chief, Biostatistics and Informatics University of Maryland School of Medicine Division of Gerontology Baltimore VA Medical Center 10 North Greene Street GR

Re: [R] Poisson regression: computation of linear combination of coefficients. Should one use the scaled var-cov matrix?

2010-01-29 Thread Peter Dalgaard
John Sorkin wrote: windows XP R 2.10 When computing the variance of a linear combination of the coefficients from a Poisson regression (i.e. glm with log link and offset) should one use the scaled or unscaled covariance matrix? For a simple linear regression (i.e. lm), I believe we use the u

Re: [R] Poisson Regression - Query

2009-09-19 Thread Achim Zeileis
On Sat, 19 Sep 2009, Axel Urbiz wrote: Hi All, My dependent variable is a ratio that takes a value of 0 (zero) for 95% of the observations and positive non-integer values for the other 5%. What model would be appropriate? I'm thinking of fitting a GLM with a Poisson ~. Now, becuase it takes non

Re: [R] poisson regression with robust error variance ('eyestud

2008-05-13 Thread Ted Harding
On 13-May-08 14:25:37, Michael Dewey wrote: > At 00:56 09/05/2008, Ted Harding wrote: >>I'd like to thank Paul Johnson and Achim Zeileis heartily >>for their thorough and accurate responses to my query. >> >>I think that the details og how to use the procedure, and >>of its variants, which they hav

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-13 Thread Michael Dewey
At 00:56 09/05/2008, Ted Harding wrote: I'd like to thank Paul Johnson and Achim Zeileis heartily for their thorough and accurate responses to my query. I think that the details og how to use the procedure, and of its variants, which they have sent to the list should be definitive -- and very he

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Ted Harding
I'd like to thank Paul Johnson and Achim Zeileis heartily for their thorough and accurate responses to my query. I think that the details og how to use the procedure, and of its variants, which they have sent to the list should be definitive -- and very helpfully usable -- for folks like myself wh

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Ted Harding
Once again, Paul, many thanks for your thorough examination of this question! And for spelling out your approach!!! It certainly looks as though you're very close to target (or even spot-on). I've only one comment -- see at end. On 08-May-08 20:35:38, Paul Johnson wrote: > Ted Harding said: >> I

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Achim . Zeileis
Paul & Ted: > > I can get the estimated RRs from > > > RRs <- exp(summary(GLM)$coef[,1]) > > > but do not see how to implement confidence intervals based > > on "robust error variances" using the output in GLM. > > > Thanks for the link to the data. Here's my best guess. If you use > the follow

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Paul Johnson
Ted Harding said: > I can get the estimated RRs from > RRs <- exp(summary(GLM)$coef[,1]) > but do not see how to implement confidence intervals based > on "robust error variances" using the output in GLM. Thanks for the link to the data. Here's my best guess. If you use the following approac

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Paul Johnson
On Thu, May 8, 2008 at 8:38 AM, Ted Harding <[EMAIL PROTECTED]> wrote: > The below is an old thread: > > On 02-Jun-04 10:52:29, Lutz Ph. Breitling wrote: > > Dear all, > > > > i am trying to redo the 'eyestudy' analysis presented on the site > > http://www.ats.ucla.edu/stat/stata/faq/relative_

Re: [R] poisson regression with robust error variance ('eyestudy

2008-05-08 Thread Ted Harding
The below is an old thread: On 02-Jun-04 10:52:29, Lutz Ph. Breitling wrote: > Dear all, > > i am trying to redo the 'eyestudy' analysis presented on the site > http://www.ats.ucla.edu/stat/stata/faq/relative_risk.htm > with R (1.9.0), with special interest in the section on "relative > risk esti

Re: [R] Poisson regression in R

2008-03-02 Thread Peter Dalgaard
glmstat wrote: > I have these questions: > (1) Use Poisson regression to estimate the main effects of car, age, and > dist (each treated as categorical and modelled using indicator variables) > and interaction terms. > (2) It was determined by one study that all the interactions were > unimportan