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When I replicated the experiment I created a security with, as closes 1.47
and 1.5 as Orea's. I, then, read David's reply, and thought if I enter 1.47
why would MS store it (internally) as 1.47000...1?David, do you mean that
at a basic binary level , MS can not store a number with infinite 0's, as
1.4700000000......and therefore has to store it as 1.47000.....1? But if it
was the case , then, could the result of a calculation EVER be equal to a
fix number? In the case of Orea's problem the result of the calculation IS 2
( and not 2.000001), if it get strored as 2.000001 then this could never be
equal to 2?? right??? In wich case, any formula of the type if( the resultat
of a calculation=a fix number(2 for instance), Do someting, Do somethin
else) will NEVER work! I am very confused.......Anyone has more thoughts on
the subject?
Herve
-----Original Message-----
From: owner-metastock@xxxxxxxxxxxxx [mailto:owner-metastock@xxxxxxxxxxxxx]On
Behalf Of David Jennings
Sent: Monday, 1 October 2001 4:42 AM
To: metastock@xxxxxxxxxxxxx
Subject: Re: Calculation error in MS
I can't say i have tried to replicate your results, but it doesn't seem
unexpected. It relates to the precision of data held in MetaStock. I'm sure
there are similar experiences in the archives. Take heart, MetaStock is not
alone in this. Other trading programs suffer from the same problem e.g.
TradeStation and also databases e.g. Microsoft SQL server. If you look at
the internal representation it may well be 2.000000001 because 1.47 was held
as 1.4700000001 say. This should not be seen as a limitation, but as
something to be aware of, especially if you are subtracting a small number
from a large number or calculating over long time periods. I would urge you
to look at the absolute tolerance, rather than the number itself. There are
a number of techniques around to get over such
----- Original Message -----
From: "SR" <raftsp@xxxxxxxxx>
To: <metastock@xxxxxxxxxxxxxxxxxx>
Sent: Monday, October 01, 2001 10:26 AM
Subject: RE: Calculation error in MS
> Hello dear friends
>
> Today I noticed the following very strange error, while back-testing with
> Metastock 6.52 for windows:
>
> Previous bar's close = 1.5
> This bar's close = 1.47
>
> All the calculations made (manually or electronically ) will agree that
the
> percentage of this change is -2
> I made an indicator for calculating the change in MS itself, which also
> agrees with this percentage:
>
> ( C - Ref(C, -1) ) * 100 / Ref(C, -1)
>
> The above returns -2 allright.
>
> So far so good.
> But the strange thing is, that when I tried to verify this percentage with
> binary or ternary indicators, they did NOT recognize the change -2% as
true!
> In fact, they consider the result as >2% !
> Here is a ternary indicator that I used for verification :
>
> perc:= ( C - Ref(C, -1) ) * 100 / Ref(C, -1);
> If(perc > -2, 1,
> If(perc < -2, -1, 0))
>
> The result returned in the above case was NOT zero (0) as it should be,
but
> one (1) which means that the change is represented by a number larger
> than -2
>
> Has anybody else experienced such a thing? Do I have a virus in my
computer?
> A math terrorist maybe? Has my MS crashed quietly?
> Can someone repeat the above experiment and tell me the results please?
>
> Thanks
> Orea
>
>
>
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