Hi Mahnaz,
First of all check whether you're using the right family error
distribution according to tour respinse varia le. If you use team
abundancea from counts you need to specify "family = poisson" in your
model.
Then AIC is used to select the best from a set of candidate models, it
is not useful to describe how well a model fits the data in an absolute
sense.
Hope it helps.
Best regards
Enrico
Inviata dal mio Dispositivo Mobile
Da: Mahnaz Rabbaniha
Inviato: 07/03/2013 16:25
A: r-sig-ecology
Oggetto: [R-sig-eco] GLM
Dear all
I want to find regression between fish larva abundance and some
abiotic factor ,i used this code:
glm(formula = mychto ~ po4 + No3 + Si + Tn)
result:
Deviance Residuals:
Min 1Q Median 3Q Max
-26.586 -18.262 -12.296 -2.949 226.229
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 67.4211 73.9781 0.911 0.371
po4 -0.2887 1.6037 -0.180 0.859
No3 0.9151 4.5261 0.202 0.841
Si -0.1145 0.4850 -0.236 0.815
Tn -1.1568 4.4818 -0.258 0.798
(Dispersion parameter for gaussian family taken to be 2444.917)
Null deviance: 63156 on 29 degrees of freedom
Residual deviance: 61123 on 25 degrees of freedom
AIC: 325.72
my question is about the acceptable this AIC, or this result with
goodness of fit?
thanks
--
Mahnaz
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