[R] drop1: warning message

[Uwe Ligges]

No idea, you may want to tell us all your calls and give a reproducible 
example as well as properly formatted code that is more readable than 
the stuff below.

I guess you omitted some other warnings that tell you about too few 
obervations to fit the model (the "fitted probabilities numerically 0 or 
1 occurred" is a weak indication that your model may be overspecified).

Best,
Uwe Ligges



On 12.01.2010 08:17, Martin Bulla wrote:
> Dear R collegues,
>
> I am new to R and do not understad the warning messages, which appear
> when I am trying to apply type III procedure to my glm:
>
>> inkm$Gamie glm.inkmZ drop1(glm.inkmZ,test="Ch")
> Single term deletions
>
> Model:
> InkMb ~ IncStart + Vol + Gamie + PC1 + PC2 + PC3 + SpotsN + PC1:SpotsN
>             Df Deviance    AIC     LRT   Pr(Chi)              9.3879
> 27.388                      IncStart    1  14.6274 30.627  5.2395
> 0.0220791 *  Vol         1  15.9723 31.972  6.5844 0.0102876 *
> Gamie       1  13.8659 29.866  4.4780 0.0343330 *  PC2         1
> 9.6899 25.690  0.3020 0.5826585    PC3         1  10.7326 26.733  1.3447
> 0.2462124    PC1:SpotsN  1  21.6517 37.652 12.2638 0.0004618 ***
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Warning
> messages:
> 1: In glm.fit(x[, jj, drop = FALSE], y, wt, offset = object$offset,  :
>    fitted probabilities numerically 0 or 1 occurred
> 2: In glm.fit(x[, jj, drop = FALSE], y, wt, offset = object$offset,  :
>    fitted probabilities numerically 0 or 1 occurred
>
> Where did PC1 disappiered?  What is the meaning of these warning messages?
>
> Similarly, I do not understand where did PCs dissapeared in the
> following calculations:
>> inkm$Gamie glm.inkm0 drop1(glm.inkm0,test="Ch")
> Single term deletions
>
> Model:
> InkMb ~ IncStart + Vol + Gamie + PC1 + PC2 + PC3 + SpotsN + Gamie:PC1 +
>      Gamie:PC2 + Gamie:PC3
>            Df Deviance    AIC    LRT  Pr(Chi)            18.368
> 40.368                   IncStart   1   26.078 46.078 7.7106 0.005490 **
> Vol        1   26.515 46.515 8.1475 0.004312 **
> SpotsN     1   18.663 38.664 0.2958 0.586537   Gamie:PC1  1   20.418
> 40.418 2.0505 0.152155   Gamie:PC2  1   18.460 38.460 0.0919 0.761818
> Gamie:PC3  1   19.832 39.832 1.4647 0.226180   ---
>
> Any suggestions would help me greatly.
> Best regards,
> Martin
>
>
>
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