[R-sig-eco] Warning with betareg

Highland Statistics Ltd highstat at highstat.com
Wed Oct 31 12:11:27 CET 2012 

On 31/10/2012 11:00, r-sig-ecology-request at r-project.org wrote:
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>     1. Warning with betareg (leanne heisler)
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> Message: 1
> Date: Tue, 30 Oct 2012 12:59:09 -0500
> From: leanne heisler <leanneheisler at hotmail.com>
> To: <r-sig-ecology at r-project.org>
> Subject: [R-sig-eco] Warning with betareg
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> Dear List,
>   
> I am looking for weather patterns affecting the composition of rodent communities. I have the proportions of species (DM,MV,SBV,OBPM,HM,NGM) and shrews (SHREW) from 2004 to 2011 and am using the betareg package and AIC model selection to identify which weather variables of the current year (PREC,GDD,SNOW) and/or previous year (PREC_T,, GDD_T,,SNOW_T)) are the best predictors of change in the relative abundance (% community) of each species.


I am not sure about the cause of the error....but you shouldn't do a 
regression type analysis with so few observations. General 
recommendation is to have 15-25 observations per covariate. Eight 
observations doesn't bring you that far. And certainly not 3 covariates 
with 8 observations!

Alain

>> ab
>       X     DM     MV    SBV  SHREW    OBPM      HM     NGM   PREC     GDD  SNOW PREC_T1  GDD_T1 SNOW_T1
> 1 2004 0.2583 0.1301 0.5685 0.0215 0.00291 0.00101 0.01761 301.53 1572.14  4.67  258.06 1747.26   10.00
> 2 2005 0.2539 0.1258 0.5448 0.0478 0.00541 0.00461 0.01771 373.70 1564.48 18.33  301.53 1572.14    4.67
> 3 2006 0.3595 0.1131 0.4088 0.0474 0.02551 0.01091 0.03471 235.60 1884.40 11.33  373.70 1564.48   18.33
> 4 2007 0.4839 0.3441 0.0968 0.0753 0.00001 0.00001 0.00001 290.44 1753.85 34.00  235.60 1884.40   11.33
> 5 2008 0.4632 0.2436 0.2309 0.0326 0.00001 0.00851 0.02121 294.70 1631.28 23.00  290.44 1753.85   34.00
> 6 2009 0.2600 0.3102 0.3744 0.0482 0.00211 0.00051 0.00471 257.45 1697.45 38.67  294.70 1631.28   23.00
> 7 2010 0.7219 0.0888 0.0947 0.0592 0.00001 0.00591 0.02961 386.45 1459.83 33.00  257.45 1697.45   38.67
> 8 2011 0.3204 0.4611 0.1222 0.0463 0.04811 0.00191 0.00001 214.30 1662.87 72.00  386.45 1459.83   33.00
>
> I have successfully modeled all species up to OBPM, but have run into a warning message that I haven't been able to decipher (below).
>   
>> library(betareg)
>> betareg <- betareg(OBPM ~ GDD_T,, data=ab)
> Error in while (testhalf & stepFactor < ))) { :
> missing value where TRUE/FALSE needed
> In addition: Warning message:
> In sqrt(wpp) : NaNs produced
>
> I'm sure this is something simple, but if anyone could help me with this it would be greatly appreciated.
>   
> Thank you in advance,
> ---------------
>   Leanne Heisler
>   Graduate Student
>   Department of Biology
>   University of Regina
> Canada 		 	   		
>
>
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> End of R-sig-ecology Digest, Vol 55, Issue 12
> *********************************************
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-- 

Dr. Alain F. Zuur
First author of:

1. Analysing Ecological Data (2007).
Zuur, AF, Ieno, EN and Smith, GM. Springer. 680 p.
URL: www.springer.com/0-387-45967-7


2. Mixed effects models and extensions in ecology with R. (2009).
Zuur, AF, Ieno, EN, Walker, N, Saveliev, AA, and Smith, GM. Springer.
http://www.springer.com/life+sci/ecology/book/978-0-387-87457-9


3. A Beginner's Guide to R (2009).
Zuur, AF, Ieno, EN, Meesters, EHWG. Springer
http://www.springer.com/statistics/computational/book/978-0-387-93836-3


4. Zero Inflated Models and Generalized Linear Mixed Models with R. (2012) Zuur, Saveliev, Ieno.
http://www.highstat.com/book4.htm

Other books: http://www.highstat.com/books.htm


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