Hello Richard - Hope you don't think I'm talking down to you but if you're in
this for the long run this is what I would do (I did)
1) I purchased a product called InfoSelect and have collected about several
years of clips and programs that looked interesting. IS is from Microlog.
Has been around for many years. It's an info database and indexes every
character of every thing you clip and paste into the system.
2) Understand how AB stores the data, a time series or arrays. Functions
process and return arrays and scalars and the function description will let you
know. ValueWhen returns an array and LastValue returns a scalar or number as
documented in AB.
3) Use Explore - one of the best ways to "see" what's happening. Like so.
Hope this helps
Joe
An Exploration Example
Filter = 1;
Array1 = ValueWhen(Close> Open, DateTime());
Array2 = ( ValueWhen( Status("firstbarinrange"),BarIndex() ) );
Array3 = ( ValueWhen( Status("lastbarinrange"),BarIndex() ) );
AddColumn(DateTime(),"Date",formatDateTime);
AddColumn( Array1, "Date when Close > Open", formatDateTime );
AddColumn(Array2,"Numb2");
// Meets the condition only at the last bar in the range FROM TO setting -
change the range to demonstrate
AddColumn(Array3,"Numb3");
// A number and doesn't change over the Explore
AddColumn(LastValue(DateTime()),"Last Date",formatDateTime);
//
====================================================================================================
1st Sample Clip
dt = DateTime();
Price1 = LastValue( ValueWhen(dt==StrToDateTime("12/05/2005"), C ) );
Price2 = LastValue( ValueWhen(dt==StrToDateTime("1/06/2006"), C ) );
Price3 = LastValue( ValueWhen(dt==StrToDateTime("2/07/2007"), C ) );
AddColumn(Price1 ,"Dec 5, 2005");
AddColumn(Price2 ,"Jan 6, 2006");
AddColumn(Price3 ,"Feb 7, 2007");
2nd Clip Example
// Get the start and end bar indexes
start = LastValue( ValueWhen( Status( "firstbarinrange" ), BarIndex() ) );
end = LastValue( ValueWhen( Status( "lastbarinrange" ), BarIndex() ) );
3rd Clip
// End User Variables
// ----------------------------------
StartBar = LastValue( ValueWhen( Status("firstbarinrange"),BarIndex() ) );
FinishBar = LastValue( ValueWhen( Status("lastbarinrange"),BarIndex() ) );
----- Original Message -----
From: richpach2
To: [email protected]
Sent: Friday, October 24, 2008 12:34 AM
Subject: [amibroker] AFL example request
Hello,
Can someone please post a simple example for ValueWhen and LastValue
functions? I looked at the Function Reference Guide and still do not
get it. All AFL examples where these functions are used are too complex
to interpret in context of entire code. I just need something that
shows how to use each function and highlights the difference between
them.
Kind Regards
Richard
