fill up the null value using the previous value by grouping

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1

so I have a table 

date, sym, val 

where unfortunately, the 3rd entry sometimes is null. In that case, I want the previous value filling it up. 

I understood I could use “fills”. But I wonder why below doesn;t work? 

table: update val: prev val by sym from table where null val; 

2

Hi,

Think you will need to have:

update val:(fills;val) fby sym from t

the “where null val” part of your statement will return the number of rows that you have nulls in your val col, and then you set val:prev val which is not there therefore when you update there’s no change.

Marcus 

—
Sent from Mailbox

On Wed, Nov 4, 2015 at 1:44 PM, ZCodeNoob <jieyunfu@gmail.com> wrote:

so I have a table 

date, sym, val 

where unfortunately, the 3rd entry sometimes is null. In that case, I want the previous value filling it up. 

I understood I could use “fills”. But I wonder why below doesn;t work? 

table: update val: prev val by sym from table where null val; 

–
Submitted via Google Groups

3

t1:(sym:10#ab;p1:til 10);

t1:update p1:0Nj from t where i in 2 3 6 7;

t2:update p2:fills p1 by sym from t1;

t3:update p2:(fills;p1) fby sym from t1;

t2~t3 / true


q)t2

sym p1 p2

---------

a 0 0

b 1 1

a 0

b 1

a 4 4

b 5 5

a 4

b 5

a 8 8

b 9 9