[soheir]

This might be what you’re looking for then

q) x1:(`Col1;12;.z.Z) 
q) x2:(`Col1;12;`ERROR) 
q) show y:(x1;x1;x1;x2) 
`Col1 12 2021.12.08T17:46:26.162 
`Col1 12 2021.12.08T17:46:26.162 
`Col1 12 2021.12.08T17:46:26.162 
`Col1 12 `ERROR 
q) {x,@[gtime;last x;0Np]}each y 
`Col1 12 2021.12.08T17:46:26.162 2021.12.08T17:46:26.162 
`Col1 12 2021.12.08T17:46:26.162 2021.12.08T17:46:26.162 
`Col1 12 2021.12.08T17:46:26.162 2021.12.08T17:46:26.162 
`Col1 12 `ERROR 0Np

 

[soheir]

Hi @ekallivrousis, try using a vector conditional – https://code.kx.com/q/ref/vector-conditional/

update c:?[b;`true;`false] from t

b = vector of booleans being passed in

[soheir]

Hey @ekallivrousis – is this what you’re trying to do?

q)x:(`Col1;12;.z.Z)
q)y:(x;x;x)

`Col1 12 2021.12.08T17:33:36.400
`Col1 12 2021.12.08T17:33:36.400
`Col1 12 2021.12.08T17:33:36.400
q)y,'gtime .z.P

`Col1 12 2021.12.08T17:33:36.400 2021.12.08D17:33:47.617397000
`Col1 12 2021.12.08T17:33:36.400 2021.12.08D17:33:47.617397000
`Col1 12 2021.12.08T17:33:36.400 2021.12.08D17:33:47.617397000

Or are you looking to use the last item of each list of y (list of lists) as an input to gtime ?