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Doing a few of those 12 oz curls myself. Just read your comments below
and it's all perfectly clear now. Thanks a bunch for helping me put
this all together!
Pete :-)
--- In amibroker@xxxxxxxxxxxxxxx, "Steve Dugas" <sjdugas@xxx> wrote:
>
> Hi Pete - see my comments inserted below...
>
> Steve
>
> ----- Original Message -----
> From: "Pete" <dryheat3@xxx>
> To: <amibroker@xxxxxxxxxxxxxxx>
> Sent: Saturday, August 09, 2008 8:49 PM
> Subject: [amibroker] Re: Using Functions to Process Arrays
>
>
> > Thanks for the ideas. Let me explain what I am trying to grasp. I'll
> > show the sample given in the AB help file once again.
> > Ok, so in the function below there is a loop but before the loop I see
> > the two lines:
> > <<result[ 0 ] = input[ 0 ];>>
> > <<result[ 1 ] = input[ 1 ];>>
> >
> > Now, in my mind this is creating an array. In VBA code you create
> > arrays by declaring a variable and assigning each element of the array
> > by using (0), (1), (2)... and so on. You then use this same method to
> > reference the individual elements in the array. So the way I read
> > these two lines is like this.
> > Assign Variable 'result' Element 1 = F-Argument 'input' Element 1
> > Assign Variable 'result' Element 2 = F-Argument 'input' Element 2
> >
> > So far so good? This is where I'm confused. if you have input[0] and
> > input[1] available at the time of execution, then the argument 'input'
> > must be an array to begin with. Tell me if I'm wrong.
>
> You are right! This sort of stuff sometimes confuses the experienced
> programmers more than the newbies because they have to unlearn the
way they
> have been programming for years. AFL is an array-based language,
everything
> is automatically an array, and if it isn't then it is automatically
> converted to one when necessary. Once you get the hang of it, it really
> simplifies things! It starts with your data, which are arrays. So,
if you
> then just write
>
> MyClose = Close; // now you have created a new array, MyClose.
>
> I think about the only times you need to refer to individual
elements are if
> you want to set/get the value of that specific element, or if you
are using
> recursive methods ( since regular AFL operates on the entire array
at once,
> it cannot refer to previous values of itself because all elements are
> created at the same time, hence the need for looping in that case )
>
> >
> > So, next is the loop:
> > <<for( i = 2; i < BarCount; i++ )>>
> >
> > So I understand the 'i' is used to iterate through each element of the
> > array. At this point I have to assume 'input' is an array passed to
> > the function and the loop uses the first two elements of this array to
> > calculate and return a value. Here is where I am lost. Considering the
> > most likely candidate for 'input' would be the array of the closing
> > price of the stock, how can this thing work if it only uses the values
> > for the first two bars in the array [0] and [1]?
>
>
> In this case, the formula is recursive ( the value of each element
depends
> on the value of the preceding 2 elements ). For this, looping is
needed as
> explained above. So the first 2 lines are just to initialize the
first 2
> elements, as those values are used inside the loop. After that, the
looping
> code will create the required values for each new element as it
walks the
> array, and those values will be used for future elements...anyway, its
> Saturday night and I need to get my exercises in - 12 oz curls! 8
- ).
> Will be back later!
>
>
>
> >
> >
> >> function IIR2( input, f0, f1, f2 )
> >> {
> >> result[ 0 ] = input[ 0 ];
> >> result[ 1 ] = input[ 1 ];
> >>
> >> for( i = 2; i < BarCount; i++ )
> >> {
> >> result[ i ] = f0 * input[ i ] +
> >> f1 * result[ i - 1 ] +
> >> f2 * result[ i - 2 ];
> >> }
> >>
> >> return result;
> >> }
> >> //end code ***************************************
> >
> >
> >
> >
> > --- In amibroker@xxxxxxxxxxxxxxx, "Steve Dugas" <sjdugas@> wrote:
> >>
> >> Hi again - just had another look at your question, I notice that you
> > just
> >> refer to "processing arrays". You picked an example that uses
> > looping but
> >> you can wrap any AFL in a function, you don't need to use looping
> > unless you
> >> really need it...Thnk of the function as sort of a container - it
will
> >> basically hold any code that you could just as easily put inline,
> > not much
> >> reason to use one I don't think unless you want to call the code from
> >> several places or it is part of some larger organizational scheme...
> >>
> >> Steve
> >>
> >> ----- Original Message -----
> >> From: "Steve Dugas" <sjdugas@>
> >> To: <amibroker@xxxxxxxxxxxxxxx>
> >> Sent: Saturday, August 09, 2008 7:18 PM
> >> Subject: Re: [amibroker] Using Functions to Process Arrays
> >>
> >>
> >> > Hi - Don't know of any tutorial but not sure you really need one.
> > Do you
> >> > understand basic looping already? You could start with any inline
> > looping
> >> > code. Once you have that working and understand it, you can just
> > wrap it
> >> > in
> >> > a function and pass it the arrays it needs via the function args.
> > Also,
> >> > make
> >> > sure the function is defined before it is called. I believe there
> > are a
> >> > couple of of looping tutorials in the files section, I wrote a
> > very brief
> >> > one and I think it was GP that wrote a better one. If you have
> > something
> >> > you
> >> > can't get to work, feel free to post it...
> >> >
> >> > Steve
> >> >
> >> > ----- Original Message -----
> >> > From: "Pete" <dryheat3@>
> >> > To: <amibroker@xxxxxxxxxxxxxxx>
> >> > Sent: Saturday, August 09, 2008 6:37 PM
> >> > Subject: [amibroker] Using Functions to Process Arrays
> >> >
> >> >
> >> >>I have a bit of experience with building functions in VBA so I
get the
> >> >> basic concept. But the projects I've built in the past did not
rely
> >> >> heavily on processing arrays within functions. What I would really
> >> >> like is to get my brain around this so I understand exactly what's
> >> >> taking place and, hopefully, to better apply this technique to
my AFL
> >> >> coding.
> >> >> From the AB help files:
> >> >> I simple function for a second order smoother:
> >> >> //begin code ************************************
> >> >> function IIR2( input, f0, f1, f2 )
> >> >> {
> >> >> result[ 0 ] = input[ 0 ];
> >> >> result[ 1 ] = input[ 1 ];
> >> >>
> >> >> for( i = 2; i < BarCount; i++ )
> >> >> {
> >> >> result[ i ] = f0 * input[ i ] +
> >> >> f1 * result[ i - 1 ] +
> >> >> f2 * result[ i - 2 ];
> >> >> }
> >> >>
> >> >> return result;
> >> >> }
> >> >> //end code ***************************************
> >> >>
> >> >> Do any of you know where I can get a quick and easy tutorial on
> >> >> processing arrays in functions so I can better understand how this
> >> >> looping works?
> >> >>
> >> >> Pete :-)
> >> >>
> >> >>
> >> >> ------------------------------------
> >> >>
> >> >> Please note that this group is for discussion between users only.
> >> >>
> >> >> To get support from AmiBroker please send an e-mail directly to
> >> >> SUPPORT {at} amibroker.com
> >> >>
> >> >> For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> >> >> http://www.amibroker.com/devlog/
> >> >>
> >> >> For other support material please check also:
> >> >> http://www.amibroker.com/support.html
> >> >> Yahoo! Groups Links
> >> >>
> >> >>
> >> >>
> >> >>
> >> >
> >> >
> >> >
> >> > ------------------------------------
> >> >
> >> > Please note that this group is for discussion between users only.
> >> >
> >> > To get support from AmiBroker please send an e-mail directly to
> >> > SUPPORT {at} amibroker.com
> >> >
> >> > For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> >> > http://www.amibroker.com/devlog/
> >> >
> >> > For other support material please check also:
> >> > http://www.amibroker.com/support.html
> >> > Yahoo! Groups Links
> >> >
> >> >
> >> >
> >> >
> >>
> >
> >
> >
> > ------------------------------------
> >
> > Please note that this group is for discussion between users only.
> >
> > To get support from AmiBroker please send an e-mail directly to
> > SUPPORT {at} amibroker.com
> >
> > For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> > http://www.amibroker.com/devlog/
> >
> > For other support material please check also:
> > http://www.amibroker.com/support.html
> > Yahoo! Groups Links
> >
> >
> >
> >
>
------------------------------------
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