R-alpha: problem adding a variable to an object

Murray Keir (mjk@maths.uq.oz.au)
Thu, 12 Dec 1996 15:52:21 +1000 (EST)


Date: Thu, 12 Dec 1996 15:52:21 +1000 (EST)
From: Murray Keir <mjk@maths.uq.oz.au>
To: R-testers@stat.math.ethz.ch
Subject: R-alpha: problem adding a variable to an object

I have been trying to add the variable dispersion to the glm object.  
The change works properly until the value of dispersion is actually 
assigned in the command (i.e. glm.eg <- glm(y~x,dispersion=2)
At this point, the following error appears.

Error: Mismatched dimensions in model.frame

I have tracked down the source of the error to the statement

        mf <- eval(mf, sys.frame(sys.parent()))

in the glm function.  However, I do not know what this is doing.

Any advice on what this command does or, even better, why the error 
itself is occuring would be greatly appreciated.

Murray Keir
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