[R] glm help - final predictor variable NA

[Ben Bolker]

matthewjones43 <matthew.jones <at> kellogg.ox.ac.uk> writes:

> 
> Hi, I am not a statistician and so I am sure whatever it is I 
> am doing wrong
> must be an obvious error for those who are...Basically I can
>  not understand
> why I get NA for variable 'CDSTotal' when running a glm? 
> Does anyone have an
> idea of why this might be happening?

It might be useful to look at 
http://stackoverflow.com/questions/7337761/
 linear-regression-na-estimate-just-for-last-coefficient/7341074#7341074

(broken URL).  You are overfitting the model by including
a predictor that can be expressed as a linear combination of
other predictors, and R is trying to handle it automatically.