# R-beta: More glm bugs

**Martin Maechler
**
Martin Maechler <maechler@stat.math.ethz.ch>

*Tue, 6 Jan 1998 11:36:18 +0100*

>>>>>* "Jim" == Jim Lindsey <jlindsey@luc.ac.be> writes:
*
Jim> 1. The null degrees of freedom do not allow for observations weighted
Jim> out although the residual df do.
Jim> in glm.fit(), line. 271, change to
Jim> nulldf <- nobs-qs.numeric(intercept)-sum(weights==0)
Jim> similar to the following line for residual df
Jim> 2. in print.glm(), I do not know what "Total df" means. At present, it
Jim> is the length of the residal vector, hence not allowing for
Jim> observations weighted out, which does not make much sense. Logically,
Jim> it should be the df for the null deviance that follows directly and
Jim> this is how students here tend to interpret it. Hence, I suggest that
Jim> line 286 be changed to
Jim> cat("\nDegrees of Freedom:",x$df.null,"Total;",
Jim> etc.
Jim> 4. The problem with names of coefficients being mixed up when there
Jim> is aliasing, that I have pointed out for some time with each new
Jim> release, is still not corrected in 0.61. The fix is in the archives
Jim> (move the 4 or 5 lines that shift names outside the iteration loop in
Jim> glm.fit)
I'm fixing these three (above). They should be in the next release
(0.61.patched aka 0.61.1)
----
The following, I think is more a problem of model.matrix(.) and such lower
level functions which I leave for Thomas and Ross ...
Jim> 3. The following two lines should produce the same result but don't:
Jim> glm(y~x1:x2:x3-x1:x2:(1+x3))
Jim> glm(y~x1:x2:x3-x1:x2:-x1:x2:x3)
Jim> Only the second gives the correct answer. I have not tried to fix this.
-- Martin
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