[vkennedy]

Hi,

For wj, the prevailing quote on entry to the window is considered valid as quotes are a step function.

See this link for more details.

Window join | Reference | kdb+ and q documentation – Kdb+ and q documentation (kx.com)

[vkennedy]

Hi,

You can define a dictionary with the default values that you would like to assign and then use the fill operator to assign these values when the key is missing or the value is null.

q)ddef:enlist[`d]!enlist 99 

q)d:`a`b`c!("";2;3) 

q)(ddef^d)`d 99

Fill operator, fills keyword  replace nulls in a vector | Reference | kdb+ and q documentation – Kdb+ and q documentation (kx.com)

[vkennedy]

Hello,

To modify the table in place, pass it by name (i.e. `t).

9. Queries q-sql – Q for Mortals (kx.com)

q)t:([]c1: 1 2 3 4 5 6 7 8 9) 

q)update c2:((prev(c1)+10) + c1)%2 from `t `t 

q)update c2:((prev(c2)+10) + c1)%2 from `t `t 

q)t 
c1 c2 
-------- 
1 2 
3 9.75 
4 10.75 
5 11.75 
6 12.75 
7 13.75 
8 14.75 
9 15.75

 

[vkennedy]

Hi,

Is this the result you are looking for?

q)select c2:(0^(prev(c2)+10) + c1)%2 from update c2:((0^prev(c1)+10) + c1)%2 from t 
c2 
----- 
0 
6.25 
9.75 
10.75 
11.75 
12.75 
13.75 
14.75 
15.75

In this case, you need to explicitly fill in the zero as the result of prev on the first item of a list is null.

Appendix A. Built-in Functions – Q for Mortals (kx.com)

[vkennedy]

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