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Try this:
---8<---------------------------------
value:=C; { any value or formula }
StDay:= 02; { start Day, 1~31 }
StMnth:=01; { " Month, 1~12 }
StYear:=2004; { " Year, eg 2004 }
date:=Year()>StYear
OR (Year()=StYear AND (Month()>StMnth
OR Month()=StMnth AND DayOfMonth()>=StDay));
date:=date AND Alert(date=0,2);
ValueA:=LastValue(ValueWhen(1,date,value));
ValueB:=LastValue(ValueWhen(1,date,Ref(value,-1)));
ValueA;ValueB
---8<---------------------------------
jose '-)
--- In equismetastock@xxxxxxxxxxxxxxx, "deepfoobar" <deepfoobar@xxxx>
wrote:
> Roy,
>
> As always you have given a heck of a lot here. BTW I'm signing up
for
> your site/
> newsletter. Least that can be done for all the help you have
offered.
> (Hint Hint folks).
>
> I'm going to give this a shot for sure. But I think the problem is
> pretty fundamental
> and perhaps one that is very tough to deal with in MS as it is since
> it has no loop
> control or assingment as in other languages.
>
> What I really want to do in the example is pluck one value (in this
> case the close) on a
> given date. The date here is the first trading day of 2004. Why? I'm
> trying to evolve
> some Year-to-date indicators more for scanning purposes in the
> Explorer than for
> charting.
>
> So what I really am trying to do is pluck valueA from Jan 2, 2004
and
> then compare it
> to the valueB (in this case the close of the prior day or today).
The
> math bit in my
> example is just to display a percent change value between those
dates.
>
> Here is the pseudo-code:
>
> valueA:= the closing price on Jan 2, 2004
>
> this is all I am interested in, and once assigned I don't want
valueA
> to have any other
> value. see note below
>
> valueB:= C, today's close
>
> Now, here is the issue I have always had trouble with in MS. In
other
> languages I can
> pluck a value from a matrix or list and that's the end of it. The
> variable is assigned
> that value, end of story, no loop control necessary.
>
> In MS however since the if/then structure always seems to require an
> else valueA over
> the variable value's range goes something like this when I get it
> back from the
> formula I sent.
>
> <----- valueA
>
> Jan 2, 2004: 39.00
> Jan 5, 2004: 0
> ...
> Today's date:0
>
> ------ >
> What I want though is a variable that has only the first non-zero
> value (Jan 2 in this
> case though it could be any date of choosing). Period. Yet MS seems
> to offer no way
> to do that.
>
> The problem is that if I want to use this value in an exploration, I
> have to somehow
> parse it to get the non-zero, Jan 2nd value and then do the
> manipulation.
>
> The only other MS approach I can think of is to somehow copy the one
> value I want
> over the entire range of values. In other words every value over
the
> range of dates for
> valueA would be 39 to use the example above. Or somehow coerce the
> non-zero
> value so that it would be the LastValue() of the variable.
>
> Hope I have not utterly confused you. And maybe ValueWhen will do
it.
>
>
> --- In equismetastock@xxxxxxxxxxxxxxx, "Roy Larsen" <rlarsen@xxxx>
> wrote:
> > deepfoobar
> >
> > I've looked at your code and I can't see what it is that you're
> trying to achieve (my
> problem, not
> > yours). However from your comments I think the function you need
is
> ValueWhen().
> The trick with
> > ValueWhen() is to create an "EXPRESSION" that was last true on the
> bar that has the
> value you want
> > to record.
> >
> > So if I wanted to extend the active value of your indicator from 2
> January 2004 to
> the current bar I
> > would change your last line by naming the variable, then add
> ValueWhen() like so.
> >
> > x:=If((Start<>End),varPercent+(100*(varC-(varB+C))/varC),0);
> > ValueWhen(1,x>0,x);
> >
> > To get this to plot on a chart properly when unscaled you might
> need to add an
> "initialisation"
> > signal. The purpose of this is to trigger the ValueWhen() at the
> beginning of the
> chart. The value
> > returned by that trigger is replaced by the genuine trigger from
> the set data, but
> you need to
> > remember that the pseudo (initialisation) trigger will create a
> value even if the date
> signal does
> > not occur for whatever reason.
> >
> > ValueWhen(1,Cum(x>-1)=1 OR x>0,x);
> >
> > Now, suppose your trigger signal was true for many bars, a date
> range for example,
> and you only
> > wanted the last true bar as the real signal. No change is
necessary
> to the
> ValueWhen() because it
> > will trigger on every bar up to the last true trigger bar. If you
> wanted to return the
> value from
> > the first bar of the date range then you need to convert the
signal
> into a "leading
> edge" only
> > signal.
> >
> > ValueWhen(1,Cum(x>-1)=1 OR (x>0 AND Alert(x=0,2)) ,x);
> >
> > Notice how I've used (x>0 AND Alert(x=0,2)) to create the leading
> edge signal. you
> could use
> > Ref(x,-1)=0 in place of Alert(), but in doing so you would
> invalidate the
> initialisation expression
> > because it is active while Ref(x,-1)=0 is still invalid. An
invalid
> bar in an any
> expression in a
> > variable makes the whole variable invalid.
> >
> > Hope this helps.
> >
> > Roy
> >
> > > I have run into an annoying issue with MS I need help with.
> Following
> > > Roy Larsen's example I've been able to write some date code that
> works
> > > well in isolating the start and end of data to look at.
> > >
> > > The recent issue is that I want to be able to grab a value from
a
> date
> > > and return that value in a variable to use in explorations.
> > >
> > > Right now I have the code set up so that I get the expected
value
> on
> > > the specific date and zero otherwise. That works fine as far as
> plots
> > > go, but stops me dead in my tracks when it comes to using the
> variable.
> > >
> > > Here is the code such as it is:
> > > << ---------------
> > >
> > > Sd:=2;
> > > Sm:=1;
> > > Sy:=2004;
> > >
> > > Start:=(DayOfMonth()>=Sd AND Month()=Sm AND
> > > Year()=Sy);
> > >
> > > End:=(DayOfMonth()>=Sd+1 AND Month()=Sm AND
> > > Year()=Sy);
> > >
> > > varB:=0;
> > > varPercent:=0;
> > > varC:=LastValue(C);
> > >
> > > If((Start<>End),varPercent+(100*(varC-(varB+C))/varC),0)
> > >
> > > ------------------- >>
> > >
> > > Is there a way to isolate a variable only to the non-zero result
> (this
> > > would be varPercent)? The problem seems to be near as I can tell
> that
> > > I must be getting only the last value back from this instead of
> the
> > > variable, and thus always zero.
> > >
> > > In other languages this would be a snap. I'm at a loss in how to
> tell
> > > MS not to stomp all over this and return the non-zero result.
> > >
> > > Hope this was resonably clear. I want the variable back in
> isolation
> > > for that date by the way to use in other calculations. It is not
> > > necessary for it to be plotted at all really.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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