[R-sig-eco] Warning with betareg

[leanne heisler]

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. 

>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