How can I replace the values in the first n columns of my table？
i.e. mycol:(1 2 3 4) to mycol:(a a 3 4)
Thank you in advance!
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If it's the values within mycol that you want updated then they will need to be of the same type as the existing values. See below.
q)t:([]mycol:`$string 1+til 4;mycol2:til 4)
q)update mycol:`a from t where i<2
mycol mycol2
------------
a 0
a 1
3 2
4 3
One way around this though is to enlist mycol, that way updates of any type can be made.
q)t:([]mycol:1+til 4;mycol2:til 4)
q)update mycol:`a from(update enlist each mycol from t)where i<2
mycol mycol2
------------
`a 0
`a 1
,3 2
,4 3
q)meta update mycol:`a from(update enlist each mycol from t)where i<2
c | t f a
------| -----
mycol |
mycol2| j
It's unclear from your question whether you want the column names or the column values changed. If it's the column names, you can use xcol.
q)(2#`a)xcol([]w:3#til 3;x:3#.Q.a;y:`;z:0N)
a a y z
-------
0 a
1 b
2 c
Cathal O'Neill
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For follow up, I think what I am trying to do is to replace the first entries in my column with null while keeping the remaining entries the same. I am not sure how to do that – Emily Wilson Mar 26 '21 at 15:51
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What is the type of the column? – Cathal O'Neill Mar 26 '21 at 15:56
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They are float. I figured out just now tho. Thank you!! – Emily Wilson Mar 26 '21 at 16:54
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@EmilyWilson Please don't forget to mark the answer. – Jeter-work Mar 28 '21 at 01:38