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Roy,
Yuou are excatly right. The IsDefined and IsUndefined functions are complete
misnomers. I had posed a question to Equis tech support over 2 years ago
about them, and their response was:
==============================
IsDefined is a true or false signal. However both true and false have to be
possible values in the chart. IsDefined will illustrate graphically those
periods within a chart where the formula is defined and where it is not
defined.
For example load a chart with 400 days.
Plot the formula IsDefined(MOV(C,200,E)) in this chart. You will see this
indicator graph displays a 0 for the first 199 periods of this
chart and plots a +1 day 200 to day 400 in the chart. IsDefined is a
way to see within a chart where the indicator would not return a value and
where it would return a value.
However IsDefined is just like any other indicator in that it cannot be used
in a chart that does not have at least enough data to calculate the value of
the formula it encloses at least one time so that it can identify when it is
defined compared to when it is not defined.
==============================
They basically treat it as a True or False argument but do not allow a
substitute to be selected in case of False. A complete dead end.
Regards
JD
PS: A suggestion for your book title: Metastock Tips & Tricks
From: "Roy Larsen" <rlarsen@xxxxxxxxxxxxxx>
Reply-To: equismetastock@xxxxxxxxxxxxxxx
To: <equismetastock@xxxxxxxxxxxxxxx>
Subject: Re: [EquisMetaStock Group] Re: ROY'S BOOK
Date: Thu, 4 Sep 2003 14:02:47 +1200
Hi Preston
> Now to the answer...this works for me. The more I thought about the
> barcount the more I liked the idea. I have no experience with
> Isdefined() and Isundefined() so I'll have to play with it some.
These functions should, in my opinion, have an option that allows an
alternative user defined plot when the subject plot is N/A. The fact that
each function is only capable of a binary plot makes them almost useless.
Immediately the N/A plot is added (externally) to either of these functions
the very problem that they should cure pops up again. An intelligent
implementation would allow the user to specify the offending plot AS WELL AS
a substitute for when the target plot was N/A, all from within the function
itself.
You probably won't recall but my early "GE" code, developed with MS6.52,
used "Init:=Cum(N AND X >=0)=1" or something close to it as an
initialisation variable. This code is in essence the MS 6.52 version of
IsDefined(), and just as useful as far as I can see
Something like this is what I envisage for IsDefined()
IsDefined("target plot","alternative plot") {value output instead of binary
output, or possibly optional}
example.
IsDefined(Mov(C,21,E),Mov(C,Cum(1),E));
Of course Cum(1) can't be used as a constant but that's another issue.
Well there's some food for thought anyway.
Roy
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