if I define zscore as  z0 =. (- mean) % stddev, z0 works for rank 1 array.
For a rank 2 array like a=. i. 3 4, if I want to get zscore along either column 
or row, I could define
z1 =. [: |: stddev %~ |: - mean


z1 i. 3 3
_1 _1 _1
0  0  0
1  1  1

and 

z1"1 i. 3 3
_1 0 1
_1 0 1
_1 0 1

My question is that z1 uses |: twice and looks awkward. If there any clever way 
to implement z1 by rank annotation or something?
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