Filtering a Jagged Array with no fields

[MoAly98]

Hi,

This might be a stupid question, but I have an awkward array that looks like:

arr = [ [1,2,3], [4,5], ...] 

and I would like to filter/mask the inner values of the array (e.g. mask elements <= 1 such that arr -> [[None,2,3],[4,5] ). I know how to do this if I have a field, since it's a simple `arr.field > X', but in this case the array has no fields.

Is this possible?

Thank you very much.

[agoose77]

The masking and filtering features in NumPy / Awkward are actually orthogonal (unrelated) to the fields feature.

If you have an array e.g.

x = ak.Array([
    [1,2,3],
    [4, 5],   
    [6, 7, 8, 9]
])

then to mask out the elements <=1, you can just use .mask, e.g.

y = x.mask[x > 1]

The top-level function ak.mask, unlike ak.Array.mask actually accepts a valid_when argument that you can use to invert the meaning of the boolean mask array (i.e. if you want True to mean "set this value to None").

For more information on filtering and masking, I recommend reading the docs on the topic :)