CODEWITHSUNDEEP
kdb+q-lang
user8415577
user8415577

Reputation:

Returning a list of tables in kdb

There is a function in kdb generating multiple tables as results. My main aim is to analyze each of the table generated using python.

Is there a way I can make it return a list of table or some dictionary of tables so I can export it to python or should I try something else? Any leads on this is appreciated. Thanks

Upvotes: 0

Views: 2275

Answers (1)

Ryan McCarron
Ryan McCarron

Reputation: 909

It's not clear what you're asking - do you have a function which generates multiple tables? And you want to return a list of these tables? If that is the case and you have something like 

f:{t:([]a:x?`1;b:x?10);q:([]c:x?`2;d:x?10f)}

that you want to modify to return both t and q, you can just manually construct a list from within the function:

q)f:{t:([]a:x?`1;b:x?10);q:([]c:x?`2;d:x?10f);(t;q)}
q)f 3
+`a`b!(`o`p`l;5 8 5)
+`c`d!(`ig`nf`no;9.149882 9.030751 7.750292)

or alternatively, you can return the tables by using enlist on each table and joining the results of these operations:

q)f:{t:([]a:x?`1;b:x?10);q:([]c:x?`2;d:x?10f);enlist[t],enlist[q]}
q)f 3
+`a`b!(`n`a`a;6 9 0)
+`c`d!(`nn`mi`om;9.216436 1.809536 6.434637)

Or, if you use each to pass multiple inputs to a function returning a single table, the results will naturally be a list of tables:

q)f:{t:([]a:x?`1;b:x?10)}
q)f each 3 3
+`a`b!(`l`o`d;9 5 2)
+`a`b!(`h`m`g;9 5 9)

One other modification you could make is to join each table onto a table list as it's created:

q)f:{tl:();
     t:([]a:x?`1;b:x?10);
     tl,:enlist t;
     q:([]c:x?`2;d:x?10f);
     tl,:enlist q;
     tl}
q)f 3
+`a`b!(`a`l`i;1 9 1)
+`c`d!(`db`mi`la;2.371288 5.67081 4.269177)

This is quite verbose with assigning tables, but you don't need to do so directly, you could also do:

 q)f:{tl:();
      tl,:enlist ([]a:x?`1;b:x?10);
      tl,:enlist ([]c:x?`2;d:x?10f);
      tl}

To get the same output, joining each table to the list as it's created, and so returning a list of tables.

Upvotes: 3

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