Lance Boyle wrote:

On Apr 21, 2005, at 5:41 PM, Fernando.Perez@colorado.edu wrote:

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Quoting Thomas Davidoff <davidoff@haas.berkeley.edu>:

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I have a vector with min equal to 412. Why am I getting a negative mean?

Without more details, it's quite difficult to be sure. Most likely, because it's very long and of integer type (ints are 32 bit objects, so you are effectively doing mod 2^31 arithmetic with negative wraparound).

Why does Python allow modular arithmetic when the user doesn't request modular arithmetic?

To get speed, scipy must assume that if you are using an integer array then you actually are requesting modular arithmetic (to the size of the integers in question). The other option would be to silently and automatically upcast when you get too large. I don't think that is the right way to go. It would be a good idea, however, to allow the user to specify a larger type within which to accomplish a reduction. Look for this in scipy.base (the new Numeric). I'm thinking of something like add.reduce(a, Int32) or add.reduce(a, Float64) which gives a return type for the array. -Travis