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Brian:
Thanks for the detailed tips...good stuff.
You said:
>>I meant to warn you that it is not good practise to append new data to an
existing, AQ created, database for backtesting (susceptible to
corruption).... it's OK for temporary working databases (scanning for
current signals etc) ... for backtesting take a history and quarantine the
database.
This has me worried, as I am working myself not only towards backtesting on
which to depend, but for an AQ maintained db to be my working db for
O/H/L/C/V data.
Can you expand on your comment and share alternatives or options to
"maintain quality" with an AQ updated db.
Ken
-----Original Message-----
From: amibroker@xxxxxxxxxxxxxxx [mailto:amibroker@xxxxxxxxxxxxxxx] On Behalf
Of brian_z111
Sent: Friday, November 14, 2008 8:39 PM
To: amibroker@xxxxxxxxxxxxxxx
Subject: [amibroker] Re: Another AQ Question
a) For an existing database that includes symbosl with no data:
- Tools >> Database Purify
- Select reference >> All Symbols >> select All Symbols/N ==
1, Report Missing Quotes
- Deselect other report options
- Default threshold is OK
- Analyse
- Click on column header to sort (separate Missing from No
Quotes)
- Shift/click first and last NoQuotes symbols
- Right Click and send to watchlist
Normal procedure to delete WL symbols from DB
b) For a new EOD database:
- create a new blank database
- leave AB open
- open AQ and import ticker list into AQ
- uncheck AutoImport
- set AQ dates to download one bar (quicker)
- download and symbols will record errors
- AQ >> Edit >> Toggle (switches checked symbols to non error
symbol)
- Check AutoImport
- Set download dates to required history
- Download (only symbols with data will be `pushed' to AB)
I didn't have time to check method B completely... I am pretty certain it
works ... if not tweaking it a little will get results (save filtered list
and restart database).
AFAIK you can't sort the AQ columns or delete all error symbols from the AQ
list.
I couldn't find the toggle to turn on the 'hidden' AB help manual either.
I meant to warn you that it is not good practise to append new data to an
existing, AQ created, database for backtesting (susceptible to
corruption).... it's OK for temporary working databases (scanning for
current signals etc) ... for backtesting take a history and quarantine the
database.
There are some tricks to using AQ ... a few are documented at the UKB
although the DBM section is incomplete and becoming dated now :-(
brian_z
--- In amibroker@xxxxxxxxxxxxxxx, "Ken Close" <ken45140@xxx> wrote:
>
> As I load symbols into AQ and fetch data, a bunch of symbols are
reported as
> errors, obviously symbols which have changed names or are no longer
listed.
>
> My question is whether there is a convenient way to purge the
database of
> the out of date symbols, by somehow reading the window of results
for those
> having errors, and then turning that into some mass deletion list.
>
> Does such a method exist?
>
> Thanks.
> Ken
>
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