Function scale (PR#2209)

Duncan Murdoch
Thu, 24 Oct 2002 13:07:29 -0400

On Thu, 24 Oct 2002 11:55:07 -0400, you wrote in message

>Generally speaking, I think it is poor design for software to 'surprise' the
>user, even if documentation specifies the surprising activity...   

I agree, but I don't think it's clear what would be unsurprising
behaviour here.

If you ask for scaling but no centering, how should the scale be

1. To me the obvious scale is sqrt(sum(x^2)/n).
2. R and S-PLUS use sqrt(sum(x^2)/(n-1)).
3. I think the original poster was suggesting
sqrt(sum((x-mean(x))^2/(n-1)) (but it wasn't stated explicitly, so I'm
not sure).

In a case like this, I'd say backwards compatibility wins.

Duncan Murdoch
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