[R-sig-eco] R: GLM

[Enrico Caprio]

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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