Re: [amibroker] Previous Value

["Tomasz Janeczko" <tj@xxxx>]

Hi Steve,
 
I know and would like to thank you for this. I only wanted to 
show Jeff that his problem could
be solved without PREV at all. 
BTW: I noticed that many authors just *love* PREV whileit is 
infernal because it is so slow.
In 95% cases one could write simpler and much faster formula 
without PREV.
 
 
Best regards,
Tomasz Janeczko
<BLOCKQUOTE 
>
----- Original Message ----- 
<DIV 
>From: 
Steve Wiser 

To: <A title=amibroker@xxxxxxxxxxxxx 
href="">amibroker@xxxxxxxxxxxxxxx 
Sent: Wednesday, June 20, 2001 11:26 
AM
Subject: Re: [amibroker] Previous 
Value
Tomasz:My point in sharing that code was not to 
provide a AMA but to show how to do the  'previous' thing in 
VBScript. I wanted an easy example that would not clutter up the essential 
part I wanted to show and the moving average was it.Just a 
note.SteveAt 08:46 AM 6/20/01 +0200, you wrote:>HiJeff 
and Steve,>>Yes, you can do it in VBSctipt and JScrtipt but 
there is also much easier >and faster way>of calculating any 
kind of variable-weight (adaptive) moving average using>AMA function 
:>>AMA - adaptive moving average (AFL 1.5)>SYNTAX ama( 
ARRAY, SMOOTHINGFACTOR )>RETURNS ARRAY>FUNCTION calculates 
adaptive moving average - simliar to EMA() but >smoothing factor could 
be time-variant (array).>EXAMPLE>>The example of 
volatility-weighted adaptive moving average formula:>>graph0 = 
ema( close, 15 );>fast = 2/(2+1);>slow = 
2/(30+1);>dir=abs(close-ref(close,-10));>vol=sum(abs(close-ref(close,-1)),10);>ER=dir/vol;>sc 
=( ER*(fast-slow)+slow)^2;>>graph0 = ama( close, sc 
);>>AMA works like this (pseudo-code):>// for day "i" the 
value is:>movavg[ i ] = smoothingfactor * array[ i ] + ( 1 - 
smoothingfactor ) * >movavg[ i - 1 ];>// movavg[ i - 1 ] isa 
PREVIOUS day value of movavg>>There is also a second version of 
AMA called AMA2 when you get 3 parameters:>AMA2( Array, ForwardFactor, 
FeedbackFactor ) and is equivalent to this >pseudo-code>// for 
day "i" the value is:>movavg[ i ] = forwardfactor * array[ i ] + 
feedback * movavg[ i - 1 ];>// movavg[ i - 1 ] is a PREVIOUS day value 
of movavg>>Best regards,>Tomasz 
Janeczko>>----- Original Message ----->From: 
<mailto:slwiserr@xxxx>Steve Wiser>To: 
<mailto:amibroker@xxxxxxxxxxxxxxx>amibroker@xxxxxxxxxxxxxxx>Sent: 
Wednesday, June 20, 2001 12:36 AM>Subject: Re: [amibroker] Previous 
Value>>Jeff:>>This has been done using VBScript a 
couple of times once as an example and>another as a tool for an 
indicator.>See the attached file as an 
example.>>SteveYour 
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