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Monday, December 12, 2011

How to delete un-wanted symbols from the Amibroker database ?


We often get perturbed with obsolete tickers in our Amibroker database arising due to the stock de-listing and these unwanted symbols unnecessarily clutter our database. Manually deleting each symbol is quite a cumbersome task. Here I shall tell you an easier way to do this.

(1) First you have to add all un-desired symbols to an empty watch list. You can add to any watch list of your choice but make sure it should be empty else desired tickers (already present in it) too shall get deleted.

(2) Now the question comes, how to add symbols to an empty watch list?
You shall have to write an AFL to get those symbols in the 'Automatic Analysis' window and then press the right click to choose the option 'Add all results to watchlist' to add symbols to an empty watch list.

A sample AFL is given below-

// This AFL displays all symbols with quotes till 01/01/2011 only i.e. symbols having no
 //quotes after this date.
TimeFrameSet(inDaily);
Filter=DateNum()<=1111200;
AddColumn(DateNum(),"dn",1);
AddColumn(Status("StockNum"),"no",1);
TimeFrameRestore();


If you don't know, how to write an AFL? Get it written by someone.
Or you shall have to manually add each un-desired symbol to the watch list.

(3) Now download the Delete_Tickers AFL and save it in the Amibroker/formula/custom folder.
When you shall double-click this formula in the charts-tree; a parameter window shall appear as in following picture.

Here you can choose the desired watchlist


By default, this AFL shall delete watch list number 50; you can choose any other watch list from the parameter window.

PS: please take the backup of the database before you use this AFL as deleted symbols can’t be restored.




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