[R] surrogate poisson models

Simon Bond bond at graylab.ac.uk
Tue May 4 15:26:46 CEST 1999


Dear R-help,

I'm applying the surrogate Poisson glm, by following Venables & Ripley (7.3
pp238-42). 

>overall_cbind(expand.grid(treatment=c("Pema","control"),age=c("young","adult","old"),repair=c("excellent","good","poor")),Fr=c(8,0,7,1,2,0,2,7,1,4,7,1,
0,3,2,5,1,9))
>overall$age_ordered(overall$age,levels=c("young","adult","old"))
>overall$repair_ordered(overall$repair,levels=c("poor","good","excellent"))
>overall.lm1_glm(terms(Fr~treatment*age+(treatment+age)*repair,
keep.order=T),family=poisson,data=overall)
> summary(overall.lm1)

Call:
glm(formula = terms(Fr ~ treatment * age + (treatment + age) * 
    repair, keep.order = T), family = poisson, data = overall)

.
.
.  

Coefficients:
                   Estimate Std. Error z value Pr(>|z|)    
(Intercept)         0.68441    0.28979   2.362  0.01819 *  
treatment          -0.28096    0.43716  -0.643  0.52043    
age.L               0.55595    0.42669   1.303  0.19259    
age.Q               0.03404    0.42817   0.079  0.93664    
treatment.age.L    -1.31805    0.66813  -1.973  0.04853 *  
treatment.age.Q    -0.37452    0.67332  -0.556  0.57805    
repair.L            1.53962    0.54255   2.838  0.00454 ** 
repair.Q           -0.49447    0.40128  -1.232  0.21787    
treatment.repair.L -3.93138    0.96310  -4.082 4.46e-05 ***
treatment.repair.Q -0.58937    0.62739  -0.939  0.34753    
age.L.repair.L     -2.08339    0.67093  -3.105  0.00190 ** 
age.Q.repair.L     -0.47257    0.59116  -0.799  0.42406    
age.L.repair.Q     -0.04208    0.42881  -0.098  0.92183    
age.Q.repair.Q     -0.64314    0.42800  -1.503  0.13293    
- ---
.
.
.

How do you interpret the suffixes .L  and .Q  in the  summary? I tried
redefining overall$age_ordered(.... labels=c(...)), to no avail. When the
factors are unordered, the suffixes are the labels, but the fitted model is
different.

Any help is much appreciated.


Simon Bond.
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