How to find the date and price that lowest close price occurs within certain date range ?

[bigbug]

Hi, there,

I have a table "stk_data" to contain the daily close price for all the
stocks in the market .
sym date close
-------------------------
SH600810 2012.05.17 8.01
SH600810 2012.05.16 7.89
SH600810 2012.05.15 8.1
SH600810 2012.05.14 8.36
SH600810 2012.05.11 8.35
SH600810 2012.05.10 8.16
SH600810 2012.05.09 8.12

And I want to define a function
"find_lowest[stk_data;start_date;end_date]" which output a table that
tells the date and the price that lowest close price occurs within the
period defined by the "start_date" and "end_date" . like this :

sym date_occur close
-------------------------
SH600810 2012.04.03 6.89
SH600732 2012.05.06 20.23
SH600367 2012.04.25 12.50

Can someone help to tell how to write the q code ?

Thanks,
Halley

[Fintan Quill]

select from stk_data where date within(start_date;end_date),close=(min;close)fby sym

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[bigbug]

I try "select from stk_data where date
within(2012.05.16;2012.01.01),close=(min;close) fby sym", but return
table is empty , just display the column name without any data !! (I
check the "stk_data" did have data inside.). Why ?

> >http://groups.google.com/group/personal-kdbplus?hl=en.- 隐藏被引用文字 -
>
> - 显示引用的文字 -

[Fintan Quill]

In your example start_date>end_date

Try:

select from stk_data where date within(2012.01.01;2012.05.16),close=(min;close) fby sym 

[bigbug]

Amazing !! Thank you very much. I need to learn more to catch KDB+
capability.

> > > >http://groups.google.com/group/personal-kdbplus?hl=en.-隐藏被引用文字 -

[Aaron Davies]

>> select from stk_data where date within(2012.01.01;2012.05.16),close=(min;close) fby sym
>

> Amazing !! Thank you very much. I need to learn more to catch KDB+ capability.

note that the list form (parens and semi-colon) are unnecessary with literals

select from stk_data where date within 2012.01.01 2012.05.16,close=(min;close)fby sym

[Attila Vrabecz]

not just unnecessary, but has performance penalty implications