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Stephane
Some suggestions.
1. Forget about using IsUndefined() - it's a waste of time and space unless
you use it to create the following "Initialised" (is valid) type of formula.
2. Create an "Initialised" variable that gives a one bar spike when ALL your
other formulas are valid.
I:=Cum("formula 1"+"formula 2"+"formula 3">some impossible negative #)=1;
Note that for binary variables the formula can be as simple as this
"I:=Cum((N+X)>-1)=1;"
3. Include "I OR " in all BarsSince(), HighestSince() or ValueWhen() etc.
functions.
BarsSince(I OR Fml("Wkly MACD Histogram")>0))
The "I" variable is doing all that the IsUndefined() can do for you, it will
work with 6.52 as well as it works with 8.01, and most importantly it gives
a pseudo signal that is the best possible starting point for your useful
plot. Well actually, as you know, the best starting point is bar one of the
chart, but IsDefined() and IsUndefined() are crippled functions and won't
help you achieve anything in the normal N/A plot area anyway.
The concept of the "I" variable creates a starting reference point where all
required variables are known to be valid. It is rarely of any consequence as
to what value a BarsSince() or ValueWhen() function returns at this point.
What is important is that they return ANY value other than N/A.
Roy
----- Original Message -----
From: "stephanegranger_2000" <grangers@xxxxxxxxxxxx>
To: <equismetastock@xxxxxxxxxxxxxxx>
Sent: Thursday, October 02, 2003 10:09 AM
Subject: [EquisMetaStock Group] Problem with if and isUndefined
> Hi everybody,
>
> I'm currently trying to write a system tester for the Triple Screen
> Trading system from Dr. Elder.
>
> I'm having a problem with assigning a value when IsUndefined is true.
>
> At some point, I need to compute how long the weekly MACD histogram
> has been under 0.
>
> So this is what I wrote,
>
> nbBarsSinceBelowZero :=
> If( IsUndefined(BarsSince(Fml("Wkly MACD Histogram")>0)),
> 10000,
> BarsSince(Fml("Wkly MACD-Histogram")>0));
>
> When I plot the variable nbBarsSinceBelowZero, there is a large gap
> at the beginning of the graph i.e. nbBarsSinceBelowZero is also
> undefined but I would expect it to have a value of 10000 instead.
>
> However if I write
>
> If( IsUndefined(BarsSince(Fml("Wkly MACD Histogram")>0)),
> 10000,
> 0);
>
> I get 10000 at the beginning where I was getting no value and then a
> lot of 0. So this is clearly a bug in MetaStock.
>
> Does anybody have a work around for that problem?
>
> Thank you,
> Stephane
>
>
>
>
>
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>
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>
>
>
>
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