[R-sig-eco] About data distribution model

[Nicholas Lewin-Koh]

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> Message: 1
> Date: Thu, 18 Dec 2008 16:52:46 +0530
Hi,
If your counts are relatively high, you might start with a log-normal or
gamma
distribution. What you are talking about here are species abundance
distributions
on which there is a large body of confusing (and often wrong)
literature.
A good resource is Steinhard Engen (1978), Stochastic Abundance Models,
CRC press.
But this may be hard to find these days, and is not for the beginner. 

But anyway, to just do an ANOVA, comparing treatments just taking the
log
and assuming a log-normal distribution may be good enough. By the way
what is your response? Number of species? In that case you could do

fit<-lm(log(No.Species)~Habitat, mydat)
anova(fit)
or
glm(No.Species~Habitat, mydat,family=poisson())
anova(fit)

But I am not sure this answers anything. If your habitats
follow a gradient, or you have covariates describing the habitats, you
may want to look at ordination methods in vegan or ade4

good luck

Nicholas


> From: "mujeeb rahman" <mujeebrahmanp at gmail.com>
> Subject: [R-sig-eco] About data distribution model
> To: r-sig-ecology at r-project.org
> Message-ID:
> 	<ac3840600812180322p47f58301x7face2587107c21b at mail.gmail.com>
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> 
> Hi
> I have soil fauna count data from 60 plots (locations) which comprise 15
> different habitats (15 x 4). From each of the 60 plots i taken 4 soil
> monoliths (soil core of 25 x25 cm size) and counted all the fauna. it is
> sure that the data does not follow a normal distribution and we could do
> anova.
> I want to find out which dsitribution it follow and to find out which
> model
> it can fit well. (Some body says that such type of data may fit with
> negative binomial or poisson.)
> 
> Any solutions in R?.
> More over I am new to R programme, I expect your kind help
> 
> Mujeeb Rahman P
> Kerala Forest Research Institute
> Peechi, Thrissur, Kerala, India.
> 
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