Le 26/01/2012 16:50, Pauli Virtanen a écrit :
the current behavior is not a bug, I completely agree that numpy.cov(m,y) does what it says !
I (and apparently some other people) are only questioning why there is such a behavior ? Indeed, the second variable `y` is presented as "An additional set of variables and observations". This raises for me two different questions : * What is the use case for such an additional set of variables that could just be concatenated to the first set `̀m` ? * Or, if indeed this sort of integrated concatenation is useful, why just add one "additional set" and not several "additional sets" like :
cov(m, y1, y2, y3, ....) ?
But I would understand that numpy responsibility to provide a stable computing API would prevent any change in cov behavior. You have the long term experience to judge that. (I certainly don't ;-) ) However, in the case this change is not possible, I would see this solution : * add and xcov function that does what Elliot and Sturla and I described, because * possibly deprecate the `y` 2nd argument of cov because I feel it brings more definition complication than real programming benefits (but I still find that changing cov would lead to a leaner numpy API which was my motivation for reacting to Elliot's first message) Pierre