[Numpy-discussion] please change mean to use dtype=float
oliphant at ee.byu.edu
Tue Sep 19 19:17:47 CDT 2006
Sebastian Haase wrote:
>On Tuesday 19 September 2006 15:48, Travis Oliphant wrote:
>>Sebastian Haase wrote:
>>>can we please change dtype to default to float64 !?
>>The default is float64 now (as long as you are not using
>>I suppose more appropriately, we could reduce over float for integer
>>data-types when calculating the mean as well (since a floating point is
>Is now mean() always "reducing over" float64 ?
>The svn note """Log:
>Fix mean, std, and var methods so that they reduce over double data-type with
>makes it sound that a float32 input is stays float32 ?
Yes, that is true. Only integer inputs are changed because you are
going to get a floating point output anyway.
>For mean calculation this might introduce large errors - I usually would
>require double-precision for *any* input type ...
Of course. The system is not fool-proof. I hesitate to arbitrarily
change this. The advantage of using single-precision calculation is
that it is faster. We do rely on the user who expressly requests these
things to be aware of the difficulties.
>(don't know how to say this for complex types !? Are here real and imag
>treated separately / independently ?)
There is a complex add performed at a low-level as two separate adds.
The addition is performed in the precision requested.
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