"The traditional mathematics professor of the popular legend
is absentminded. He usually appears in public with a lost umbrella
in each hand. He prefers to face a blackboard and to turn his back on
the class. He writes a, he says b, he means c, but it should be d.
Some of his sayings are handed down from generation to generation.
In order to solve this differential equation you look at it till a solution occurs to you.
This principle is so perfectly general that no particular application of it is possible.
Geometry is the science of correct reasoning on incorrect figures.
My method to overcome a difficulty is to go round it." (G. P\'olya)
The last is relevant here: This problem can be avoided by a
prior call to -egen, group()-.
Nick
[email protected]
Edwin Leuven
> Nick Cox wrote:
> > I agree with Michael that -tabstat- sounds like the
> > first port of call.
>
> -tabstat- only allows 1 byvar if i am not mistaken.
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