[R] Is AIC in glm right?

[Hiroto Miyoshi]

> Could anyone help me?
> I am doing a regression analysis using glm.
> and the glm function gives AIC at the end of 
> the output.  However, the AIC value the function
> gives does not seem right.  The details of my 
> analysis goes as follows.
> 
>  > x
>      y  x z
> 1  325  2 1
> 2  275  4 0
> 3  350  4 1
> 4  400  6 1
> 5  325  7 0
> 6  425  8 1
> 7  375 10 0
> 8  475 10 1
> 9  400 12 0
> 10 575 12 1
> 11 425 14 0
> 12 450 16 0
> 13 700 17 1
> 14 525 18 0
> 15 600 20 0
> 16 750 20 1
> 17 650 22 0
> 18 775 23 1
> 19 675 24 0
> 20 825 26 1
> 
> > glm(x$y~x$x+x$z)
> 
> Call:  glm(formula = x$y ~ x$x + x$z) 
> 
> Coefficients:
> (Intercept)          x$x          x$z  
>      148.82        21.85       131.51  
> 
> Degrees of Freedom: 19 Total (i.e. Null);  17 Residual
> Null Deviance:      533000 
> Residual Deviance: 13350        AIC: 194.8 
> 
> > a<-residuals(glm(x$y~x$x+x$z))
> > sum(a*a)
> [1] 13347.96
> > 
> 
> Now, since sum of squares of residuals of the regression 
> is 133347.96, should AIC be 136.068, 
> i.e. 20*ln(13348/20)+2*3?
> 
> Could someone help me?
> Thank you.
> ---------------------------
> Hiroto Miyoshi　（三好弘人）
> h_m_ at po.harenet.ne.jp
> 
> 
> 

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