[PYTHON MATRIX-SIG] reduce methods

[janko hauser]

If we don't change the axis to 1 we can't 'easy' subtract the mean
from a field.

Old mean (no axis=1)
>>> a
0 1 2
3 4 5
6 7 8
>>> a-M.mean(a)
-3. -3. -3.
 0.  0.  0.
 3.  3.  3.
>>> a-M.mean(a,1)
-1. -3. -5.
 2.  0. -2.
 5.  3.  1.

New mean (with axis=1)
>>> a-M.mean(a,1)
-1.  0.  1.
-1.  0.  1.
-1.  0.  1.

And the "sum of a list of numbers" is a number.
msum(a,None) => 36



Konrad Hinsen writes:
 > > In the second case, we're finding the minimum value in each row, so the
 > > result I would expect is:
 > > 
 > > 2
 > > 4
 > > 
 > > In other words, I'd expect the axis that was "reduced" to change to a length
 > > of one instead of completely going away.  Modifying Janko's min function to
 > 
 > But this is not how reduction works in Python (the built-in function
 > "reduce") or in any of the array languages I know. It's also not what
 > I would expect from a plain-English description: for me, a "sum of
 > a list of numbers" is a number, not a list of length one.
 > 
 > Konrad.
 > -- 
 > -------------------------------------------------------------------------------
 > Konrad Hinsen                          | E-Mail: hinsen@ibs.ibs.fr
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