parameterise table name

Community Support
1

Hi,

I’m wondering how to create a table with it’s name as the input to a function.

eg I would like something like this:

func:{[t] 

                      t::( date:date$();time:time$();size:float$();amount:float$());

        };

So, if I wish to create my (empty) global table say called table1 I just do this:

func[table1]      

Of course this doesn’t work. Any suggestions of how to best go about this? i.e. have an input to a function which will globally define a table with the input name.

thanks,

John.

2

Use http://code.kx.com/wiki/Reference/set:<o:p></o:p>

<o:p> </o:p>

q) func:{[t]  t set ( date:date$();time:time$();size:float$();amount:float$()); };<o:p></o:p>

q) func[`table]<o:p></o:p>

q) `table in tables<o:p></o:p>

1b<o:p></o:p>

<o:p> </o:p>

From: personal-kdbplus@googlegroups.com [mailto:personal-kdbplus@googlegroups.com] On Behalf Of John Smith
Sent: Monday, June 22, 2015 1:30 PM
To: personal-kdbplus@googlegroups.com
Subject: [personal kdb+] parameterise table name<o:p></o:p>

<o:p> </o:p>

<o:p> </o:p>

Hi,<o:p></o:p>

<o:p> </o:p>

I’m wondering how to create a table with it’s name as the input to a function.<o:p></o:p>

<o:p> </o:p>

eg I would like something like this:<o:p></o:p>

<o:p> </o:p>

func:{[t] <o:p></o:p>

                      t::( date:date$();time:time$();size:float$();amount:float$());<o:p></o:p>

        };<o:p></o:p>

<o:p> </o:p>

So, if I wish to create my (empty) global table say called table1 I just do this:<o:p></o:p>

<o:p> </o:p>

func[table1]      <o:p></o:p>

<o:p> </o:p>

Of course this doesn’t work. Any suggestions of how to best go about this? i.e. have an input to a function which will globally define a table with the input name.<o:p></o:p>

<o:p> </o:p>

<o:p> </o:p>

thanks,<o:p></o:p>

<o:p> </o:p>

John.<o:p></o:p>

<o:p> </o:p>

<o:p> </o:p>

–
Submitted via Google Groups

3

Hi John, 

The following should work. 

Marcus 

f:{[t]

         t set ( date:();time:();price:())

}

f['table]

P.s. (I had no back tick symbol on my phone so used an apostrophe for the function input in the line above)

—
Sent from Mailbox

On Mon, Jun 22, 2015 at 9:29 PM, John Smith <js610308@gmail.com> wrote:

Hi,

I’m wondering how to create a table with it’s name as the input to a function.

eg I would like something like this:

func:{[t] 

                      t::( date:date$();time:time$();size:float$();amount:float$());

        };

So, if I wish to create my (empty) global table say called table1 I just do this:

func[table1]      

Of course this doesn’t work. Any suggestions of how to best go about this? i.e. have an input to a function which will globally define a table with the input name.

thanks,

John.

–
Submitted via Google Groups

4

add a couple of params, and you have yourself a neat wee function…

f:{[t;ty;c] t set flip c!ty$:()}

/t=table name

/ty=column types

/c=column names

q)f[`tab1;“SIJC”;`c`c1`c2`c4]

q)meta tab1

c | t f a

–| -----

c | s

c1| i

c2| j

c4| c

Might be useful to you..

Thanks,

Sean

5

Thanks Sean & David!! This exactly what I need, I will test this out in the mornin.

thanks,

John.

6

Thanks Marcus. 

Sean, may I also ask, in your example:

f:{[t;ty;c] t set flip c!ty$:()}

/t=table name

/ty=column types

/c=column names

f[`tab1;“SIJC”;`c`c1`c2`c4]

Do you know what to use to initialise a list of floats, eg to replace this (see prices):

func:{[t]  t set ( date:date$();time:time$();size:float$();amount:float$();prices:()); };

The last field (prices) I’ve left not specified because I don’t know how to initialise with a list of floats. I don’t actually need to, and func works for me because on the first insert into the table I insert a list of floats to prices and the type is set.

Doing a meta on the table then shows a type F meaning list of floats i assume.

In your example, I cannot get around this problem because I have to specify some letter defining the type. I’d have thought (as seen when doing a meta) the sensible approach would be to use capital letters to specify lists of a certain type, while using small letters for the atomic types, but as seen in your example capitals are used for atom type already. Any thoughts?

regards,

John

7

This should do it.

q)f[tab1;"SIJ*";cc1c2c4] tab1
q)meta tab1

c t f a
c s
c1 i
c2 j
c4
q)meta tab1 upsert enlist cc1c2c4!(`a;1i;2j;2 3 4f)
c t f a
– -----
c s
c1 i
c2 j
c4 F

Thanks Rory

8

Just what i needed! thanks Rory.