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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/neps/missing-data.rst | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/doc/neps/missing-data.rst b/doc/neps/missing-data.rst index bc61ebe1b..051cd9351 100644 --- a/doc/neps/missing-data.rst +++ b/doc/neps/missing-data.rst @@ -301,18 +301,20 @@ As part of the implementation, ufuncs and other operations will have to be extended to support masked computation. Because this is a useful feature in general, even outside the context of a masked array, in addition to working with masked arrays ufuncs -will take an optional 'mask=' parameter which allows the use -of boolean arrays to choose where a computation should be done. -This functions similar to a "where" clause on the ufunc.:: +will take an optional 'where=' parameter which allows the use +of boolean arrays to choose where a computation should be done.:: - >>> np.add(a, b, out=b, mask=(a > threshold)) + >>> np.add(a, b, out=b, where=(a > threshold)) -A benefit of having this 'mask=' parameter is that it provides a way +A benefit of having this 'where=' parameter is that it provides a way to temporarily treat an object with a mask without ever creating a -masked array object. +masked array object. In the example above, this would only do the +add for the array elements with True in the 'where' clause, and neither +'a' nor 'b' need to be masked arrays. -If the 'out' parameter isn't specified, use of the 'mask=' parameter -will produce an array with a mask as the result. +If the 'out' parameter isn't specified, use of the 'where=' parameter +will produce an array with a mask as the result, with missing values +for everywhere the 'where' clause had the value False. For boolean operations, the R project special cases logical_and and logical_or so that logical_and(NA, False) is False, and |