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wavg implementation detail
Hi, everyone.
I have some questions about wavg function.
0 wavg 5 / 5
5 wavg 5 / 5
2 wavg 2 3 7 / 4 5 2
3 wavg 3 / 3
According to the doc, the x and y of wavg[x;y] must both be numeric lists. But for these invalid inputs, wavg still yields some results. Could anyone help me understand the results of these invalid x and y?
What’s the behavior of wavg when x and y aren’t numeric lists or they don’t conform? It seems like avg y but I’m not sure.
If you know more about wavg’s implementation detail, please help me. Thanks.
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3 Replies
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Hello Ian,
Thank you for bringing this great question to our attention.
- We can confirm that
0 wavg x
should indeed be 0n. This is a bug and will be fixed by our team. Thank you for sharing this observation.
The following is an explanation for the other cases:
- Atoms on both sides behave as if enlisted to single item vectors.
5 wavg 5 / 5 enlist[5] wavg enlist[5] /5
- An atom on one side and a vector on the other behaves as if the atom is repeated to match the length of the vector.
2 wavg 2 3 7 / 4 2 2 2 wavg 2 3 7 /4 5 2 3 wavg 3 / 3 5 2 3 wavg 3 3 3 /3
We hope our feedback is helpful for you.
Thank you again for your contribution and engagement with our KX community. We look forward to more.
Kind regards,
Leah
- We can confirm that
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Hi Leah,
Thanks for your explanation.
So for the case “0 wavg x”, it is equivalent to (0*x)%0 => 0%0=0n. It really makes sense.
Thank you and your team again.
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Todays release kdb+4.0 2021.10.01 contains a fix for the issue in your first example:
q)0 wavg 5 0n
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