• kdb+

  how to read this two symbols

  Posted by chan_chenyanj on April 9, 2022 at 12:00 am

  suppose i have a table with filed1 is list of symbol `1m`3m and filed2 is source `bbg`bbg

   

  then how should i read

   

  1. #[;1b] each count each field2 from table
  
  2. {x 1 0} each filed1 from table

  chan_chenyanj replied 8 months, 1 week ago 3 Members · 3 Replies
• 3 Replies

• 

  Laura

  Administrator

  April 9, 2022 at 12:00 am

  1. count each field2 implies each item of field2 is a list its length to be counted
  2. Similarly, the lambda {x 1 0} specifies the second and first items of a list, implying field1 is also nested

   

  q)show t:([]field1:(2+5?3)?:`$string[til 10],'"m";field2:(1+5?5)?:5?`3) 
  field1 field2 
  ------------------------------ 
  `9m`1m `dmp`gce`gdp 
  `4m`3m`9m `gce`dmp`dmp`nmo`gdp 
  `8m`9m ,`icg 
  `9m`5m`4m `icg`gce`nmo`nmo`gce 
  `0m`4m`3m `dmp`icg`icg`gce 
  q)select {x 1 0}each field1, #[;1b] each count each field2 from t 
  field1 field2 
  ------------- 
  1m 9m 111b 
  3m 4m 11111b 
  9m 8m ,1b 
  5m 9m 11111b 
  4m 0m 1111b

   

  Above:

  1. the second and first items from each list in field1
  2. a boolean true for each symbol in the field2 lists

  Alternative expression:

   

  q)select reverse each 2#'field1, not null field2 from t 
  field1 field2 
  ------------- 
  1m 9m 111b 
  3m 4m 11111b 
  9m 8m ,1b 
  5m 9m 11111b 
  4m 0m 1111b

   

• 

  chan_chenyanj

  Member

  April 9, 2022 at 12:00 am

  thanks for the reply what does #[;1b] mean

• 

  rocuinneagain

  Member

  April 11, 2022 at 12:00 am

  It is a projection on take

  q)1#1b ,1b 
  q)2#1b 11b 
  q)#[;1b] 1 ,1b 
  q)#[;1b] 2 11b

   

   

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