Re: sumskipnan(nan) = 0 ?

[gail]

On Sun Sep  9 22:29 , "James Sherman Jr."  sent:

>Now, for example, if we let C be the empty set, then we get that B = A, thus
>sum(A) = sum(B) + sum(C)  being a "reasonable" property
>           = sum(A) + sum(C)  from our assumption that C is the empty set
>hence, subtracting sum(A) from both sides.
>sum(C) = 0

This holds if sum and sumskipnan operate on sets. But that is just not useful
assumption for the nan-toolbox which deals with missing value problems. Take, 
for
example, the problem of transforming hourly to daily precipitation sums. For a
day with no reported hourly values sumskipnan in its current form would deliver
zero precipitation, which is not exactly what one expects.

G.