Gary Strangman writes: [...] > Given I'm still fuzzy on all the distinctions, perhaps someone could try to > help > me (and others?) to define all /4/ logical possibilities ... some may be > obvious > dead-ends. I'll take a stab at them, but these should definitely get edited by > others:
> destructive + propagating = the data point is truly missing (satellite fell > into > the ocean; dog ate my source datasheet, or whatever), this is the nature of > that > data point, such missingness should be replicated in elementwise operations, > and > the missingness SHOULD interfere with reduction operations that involve that > datapoint (np.sum([1,MISSING])=MISSING) Right. > destructive + non-propagating = the data point is truly missing, this is the > nature of that data point, such missingness should be replicated in > elementwise > operations, but such missingness should NOT interfere with reduction > operations > that involve that datapoint (np.sum([1,MISSING])=1) What do you define as element-wise operations? Is a sum on an array an element-wise operation? >>> [1, MISSING]+2 [1, MISSING] Or is it just a form of reduction (after shape broadcasting)? >>> [1, MISSING]+2 [3, 2] For me it's the second, so the only time where special values "propagate" in a non-propagating scenario is when you slice an array. > non-destructive + propagating = I want to ignore this datapoint for now; > element-wise operations should replicate this "ignore" designation, and > missingness of this type SHOULD interfere with reduction operations that > involve > this datapoint (np.sum([1,IGNORE])=IGNORE) Right. > non-destructive + non-propagating = I want to ignore this datapoint for now; > element-wise operations should replicate this "ignore" designation, but > missingness of this type SHOULD NOT interfere with reduction operations that > involve this datapoint (np.sum([1,IGNORE])=1) Same concerns as above. Lluis -- "And it's much the same thing with knowledge, for whenever you learn something new, the whole world becomes that much richer." -- The Princess of Pure Reason, as told by Norton Juster in The Phantom Tollbooth _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
