Dear Lawren, Stephen and the list

Thank you both for your suggestions!

This is the code ive used in R and the error. The start values are the
values derived by excel (y = 20.79e^-0.001x)

nls(CRR ~ a*exp(1)^b*Soil.Temp,
data=cloths2[cloths2$trt==1&cloths2$veg==1,], start=list(a=20.79,
b=-0.001))Error in nls(CRR ~ a * exp(1)^b * Soil.Temp, data =
cloths2[cloths2$trt ==  :
  singular gradient


and using lm (as per Stephens suggestion (I think you're correct too, I
think I saw this answer as I looking for solutions)):

lm(log(CRR)~Soil.Temp, cloths2[cloths2$veg==1&cloths2$trt==1,])
Call:
lm(formula = log(CRR) ~ Soil.Temp, data = cloths2[cloths2$veg ==
    1 & cloths2$trt == 1, ])

Coefficients:
(Intercept)    Soil.Temp
     2.6962       0.0228



Does anyone on the list have any experience of calculating Q10 in R?
Otherwise I think Im perhaps stuck.


Cheers,

Alan


--------------------------------------------------
Email: aghaynes@gmail.com
Mobile: +41794385586
Skype: aghaynes


On 30 January 2012 18:29, Stephen Sefick <sas0025@auburn.edu> wrote:

> linearize the model and fit.
>
> I think it is
> lny=lna+bx
>
> make sure I did the conversion correctly
>
> y=ae^bx
>
> take the natural log of both sides
>
> ln(y)=ln(ae^bx)
>
> ln(y)=a+ln(e^1)*bx
>
> ln(y)=a +bx
>
> Hopefully I did this right,
>
> Stephen
>
>
>
> On 01/30/2012 10:01 AM, Alan Haynes wrote:
>
>> Dear Ecology list,
>>
>> I'm trying to calculate the Q10 (temperature sensitivity) of decomposition
>> in R. I have done so in excel straight forwardly enough but I want to
>> check
>> it in R.
>> Does anyone have any ideas how to go about this?
>>
>> It is calculated as
>>
>> y_T ~ a * e^(bx_T)
>> where y is the decomposition rate at temperature T, x_T is the temperature
>> and "a" and "b" are constants. "e" is the magic number (exp(1) ; 2.7183)
>>
>> then
>>
>>  Q10 = exp(10*b)
>>
>> In excel I simply fit an exponential trend line, read off "b" from the
>> formula and then calculate Q10 as above. In R it seems to be a bit harder.
>>
>> Ive attempted to use nls() to derive the exponent but I get a completely
>> different number (when it doesnt give me a singularity error). nls()
>> doesnt
>> seem to like the "a" term either, as it seems to be this that generates
>> the
>> singularity issue.
>>
>> Does anyone know of a function, or suite of functions, for calculating
>> Q10?
>>
>> Thanks in advance,
>>
>> Alan
>>
>>
>>
>> ------------------------------**--------------------
>> Email: aghaynes@gmail.com
>> Mobile: +41794385586
>> Skype: aghaynes
>>
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>
> --
> Stephen Sefick
> ****************************************************
> Auburn University
> Biological Sciences
> 331 Funchess Hall
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> 36849
> ****************************************************
> sas0025@auburn.edu
> http://www.auburn.edu/~sas0025
> ****************************************************
>
> Let's not spend our time and resources thinking about things that are so
> little or so large that all they really do for us is puff us up and make us
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>
>                                -K. Mullis
>
> "A big computer, a complex algorithm and a long time does not equal
> science."
>
>                              -Robert Gentleman
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