[Numpy-discussion] please change mean to use dtype=float

Sebastian Haase haase at msg.ucsf.edu
Tue Sep 19 17:33:23 CDT 2006

Hello all,
I just had someone from my lab coming to my desk saying:
"My god - SciPy is really stupid ....
An array with only positive numbers claims to have a negative mean !! "?

I was asking about this before ... the reason was of course that her array was 
of dtype int32 and had many large values  to cause an overflow (wrap 
around) .

Now that the default for axis is None (for all functions having an axis 
can we please change dtype to default to float64 !?

It is really a very confusing and shocking result to get a negative mean on 
all positive values.

It has been stated here before that numpy should target the "scientist" rather 
than the programmers ...  I would argue that mean() almost always requires 
the precision of "double" (float64)  to produce usable results.

Please consider this change before the 1.0 release  ...
Sebastian Haase

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