Hi, On Wed, Jun 29, 2011 at 7:20 PM, Lluís <xscript@gmx.net> wrote:
Mark Wiebe writes:
There seems to be a general idea that masks and NA bit patterns imply particular differing semantics, something which I think is simply false.
Well, my example contained a difference (the need for the "skipna=True" argument) precisely because it seemed that there was some need for different defaults.
Honestly, I think this difference breaks the POLA (principle of least astonishment).
[...]
As far as I can tell, the only required difference between them is that NA bit patterns must destroy the data. Nothing else. Everything on top of that is a choice of API and interface mechanisms. I want them to behave exactly the same except for that necessary difference, so that it will be possible to use the *exact same Python code* with either approach.
I completely agree. What I'd suggest is a global and/or per-object "ndarray.flags.skipna" for people like me that just want to ignore these entries without caring about setting it on each operaion (or the other way around, depends on the default behaviour).
The downside is that it adds yet another tweaking knob, which is not desirable...
Oh - dear - that would be horrible, if, depending on the tweak somewhere in the distant past of your script, this:
a = np.array([np.NA, 1.0], masked=True) np.sum(a)
could return either np.NA or 1.0... Imagine someone twiddled the knob the other way and ran your script... See you, Matthew