Dear list,

I have run a generalized linear model with negative binomial 
distribution (log-link) on fish abundance data.

log(abundTot) ~ Bo + B1(topog) + B2(activity) + e

*My output is as follows**:*

summary(glmNB1)
Call: glm.nb(formula = abundTot ~ activity + topog, init.theta = 
5.431057349,
     link = log)
Deviance Residuals:
     Min       1Q   Median       3Q      Max
-3.1348  -0.7846  -0.2781   0.3097   5.3866
Coefficients:
                 Estimate Std. Error z value Pr(>|z|)
(Intercept)      2.65215    0.07810  33.958  < 2e-16 ***
activity[T.hd]  -0.04447    0.08299  -0.536   0.5921
activity[T.hfd] -0.44926    0.08884  -5.057 4.27e-07 ***
activity[T.nil]  0.07510    0.05808   1.293   0.1960
topog            0.03084    0.01546   1.995   0.0461 *
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

(Dispersion parameter for Negative Binomial(5.4311) family taken to be 1)

     Null deviance: 473.32  on 428  degrees of freedom Residual 
deviance: 428.00  on 424  degrees of freedom
AIC: 2916.3

Number of Fisher Scoring iterations: 1


               Theta:  5.431
           Std. Err.:  0.485

2 x log-likelihood:  -2904.260

*and*
anova(glmNB1)
Analysis of Deviance Table

Model: Negative Binomial(5.4311), link: log

Response: abundTot

Terms added sequentially (first to last)


          Df Deviance Resid. Df Resid. Dev  Pr(>Chi)
NULL                       428     473.32
activity  3   41.272       425     432.05 5.726e-09 ***
topog     1    4.053       424     428.00    0.0441 *
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Please can someone explain how to calculate the percentage deviance 
explained by each factor separately (i.e. topog and activity).

Kind regards,

-- 
_____________________________________________________________
Jade Maggs MSc
Assistant Scientist
Oceanographic Research Institute
Direct Tel: +27 (31) 328 8171 Fax: +27 (31) 328 8188
Cell: +27 83 515 1079 e-mail: jmaggs@ori.org.za
1 King Shaka Avenue, Point, Durban 4001 KwaZulu-Natal South Africa
PO Box 10712, Marine Parade 4056 KwaZulu-Natal South Africa
http://www.ori.org.za/staff.html#Jade
http://www.linkedin.com/pub/jade-maggs/29/917/5a0


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