[R-sig-eco] Multiple regression

2013-01-04 Thread Mario José Marques
Hi all, I have a doubt with multiple regression. I have this model: y ~ x + w + z but the response y to z is humped. I check this by plot and run: lm(y ~ z + I(z^2) # better r-square that lm(y ~ z) I'd like use this response with quadratic term in multiple regression. I think that if I use

Re: [R-sig-eco] Multiple regression

2010-06-01 Thread Gavin Simpson
On Mon, 2010-05-31 at 13:44 +1000, Zhongkui Luo wrote: Dear all, # I have the following sub-datasets of soil carbon change at four sites. There are four treatments at each site. DltC - c(-19.237, -14.857, -14.818, -14.815, -11.014, 3.349, 4.332, 3.956, -7.638, 9.469, 14.189, 13.037,

[R-sig-eco] Multiple regression

2010-05-30 Thread Zhongkui Luo
Dear all, # I have the following sub-datasets of soil carbon change at four sites. There are four treatments at each site. DltC - c(-19.237, -14.857, -14.818, -14.815, -11.014, 3.349, 4.332, 3.956, -7.638, 9.469, 14.189, 13.037, -9.809, 5.459, 8.748, 11.511) # Soil C fractions at the start of

Re: [R-sig-eco] multiple regression

2010-02-17 Thread Kingsford Jones
On Tue, Feb 16, 2010 at 11:15 PM, David Hewitt dhewit...@gmail.com wrote: Date: Sun, 14 Feb 2010 17:15:02 -0700 From: Kingsford Jones kingsfordjo...@gmail.com To: gustaf.gran...@ebc.uu.se Cc: r-sig-ecology@r-project.org Subject: Re: [R-sig-eco] multiple regression Message-ID

Re: [R-sig-eco] multiple regression

2010-02-16 Thread David Hewitt
Date: Sun, 14 Feb 2010 17:15:02 -0700 From: Kingsford Jones kingsfordjo...@gmail.com To: gustaf.gran...@ebc.uu.se Cc: r-sig-ecology@r-project.org Subject: Re: [R-sig-eco] multiple regression Message-ID:        2ad0cc111002141615w178722c7u1e47315a7b8aa...@mail.gmail.com Content-Type: text

Re: [R-sig-eco] multiple regression

2010-02-15 Thread Gustaf Granath
Sent: Saturday, February 06, 2010 5:17 PM To: r-sig-ecology@r-project.org Subject: [R-sig-eco] multiple regression Hi everyone, I'm trying to fit a multiple regression model and have run into some questions regarding the appropriate procedure to use. I am trying to compare fish

Re: [R-sig-eco] multiple regression

2010-02-09 Thread Gustaf Granath
lemoine.nat...@gmail.com Sent: Saturday, February 06, 2010 5:17 PM To: r-sig-ecology@r-project.org Subject: [R-sig-eco] multiple regression Hi everyone, I'm trying to fit a multiple regression model and have run into some questions regarding the appropriate procedure to use. I am trying

Re: [R-sig-eco] multiple regression

2010-02-08 Thread romunov
Hi Nathan, I fould this paper by Zuur and co-workers, 2009http://www3.interscience.wiley.com/journal/122683826/abstract?CRETRY=1SRETRY=0, very insightful. While step-wise modeling is something The R book presents, it may or may not be the best way to do it. Read the paper and judge for yourself

Re: [R-sig-eco] multiple regression (ONKELINX, Thierry)

2010-02-08 Thread Highland Statistics Ltd.
Message: 1 Date: Mon, 8 Feb 2010 11:02:37 +0100 From: ONKELINX, Thierrythierry.onkel...@inbo.be To: Peter Solymossoly...@ualberta.ca, Nathan Lemoine lemoine.nat...@gmail.com Cc: r-sig-ecology@r-project.org Subject: Re: [R-sig-eco] multiple regression Message-ID

Re: [R-sig-eco] multiple regression (ONKELINX, Thierry)

2010-02-08 Thread ONKELINX, Thierry
Dear Alain, Thank you for your comments. Interesting thought. Maybe correct. But there are a few things to think about: 1. You have to assume that sampling was such that all species out there have ended up in the data. Formulated differently...you need to know the N_i (maximum number of

Re: [R-sig-eco] multiple regression

2010-02-08 Thread Peter Solymos
Onderwerp: Re: [R-sig-eco] multiple regression On Mon, 2010-02-08 at 11:02 +0100, ONKELINX, Thierry wrote: Peter, I would think that the species richness is binomial distributed. Since there is a maximum number of species that can be present. Therefore I would model it like glm(cbind

Re: [R-sig-eco] multiple regression

2010-02-08 Thread Manuel Spínola
answer can be extracted from a given body of data. ~ John Tukey -Oorspronkelijk bericht- Van: Gavin Simpson [mailto:gavin.simp...@ucl.ac.uk] Verzonden: maandag 8 februari 2010 11:14 Aan: ONKELINX, Thierry CC: Peter Solymos; Nathan Lemoine Onderwerp: Re: [R-sig-eco] multiple regression

Re: [R-sig-eco] multiple regression

2010-02-08 Thread Aitor Gastón
/stats/faq/faq12.asp Cheers, Aitor -- From: Nathan Lemoine lemoine.nat...@gmail.com Sent: Saturday, February 06, 2010 5:17 PM To: r-sig-ecology@r-project.org Subject: [R-sig-eco] multiple regression Hi everyone, I'm trying to fit a multiple

Re: [R-sig-eco] multiple regression

2010-02-08 Thread Joe Fontaine
Perth, Australia 6150 j.fonta...@murdoch.edu.au From: r-sig-ecology-boun...@r-project.org on behalf of Aitor Gastón Sent: Tue 2/9/2010 2:19 AM To: Nathan Lemoine; r-sig-ecology@r-project.org Subject: Re: [R-sig-eco] multiple regression Hi Nathan, Many authors

Re: [R-sig-eco] multiple regression

2010-02-06 Thread Andrew Kosydar
Hi Nathan, I only quickly read your email, but I believe you were asking about step-wise regression. I would strongly suggest that instead you consider using multimodel inference (Burnham Anderson). If you want I can suggest for you a couple of papers to read in order to learn more about

Re: [R-sig-eco] multiple regression

2010-02-06 Thread Peter Solymos
Nathan, Species richness is categorical, so if your richness values are usually low (say 20), you should consider the use of Poisson GLM, or log-transform your response (and log is the canonical link function for Poisson GLM). This usually improves the model fit. And this might apply to

Re: [R-sig-eco] multiple regression

2010-02-06 Thread Peter Solymos
I meant Species richness is discrete, not categorical. Peter On Sat, Feb 6, 2010 at 12:52 PM, Peter Solymos soly...@ualberta.ca wrote: Nathan, Species richness is categorical, so if your richness values are usually low (say 20), you should consider the use of Poisson GLM, or log-transform