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Dimitris,
The {empty} ( or Null) in AmiBroker works as NULL in the
databases.
When any part of arithmetic expression is NULL the entire
expression becomes NULL.
Null (empty) means in fact "UNKNOWN"
If you add 2 + UNKNOWN the result is
still UNKNOWN.
For example for the first 20 bars the value of MA( Close, 20 )
is UNKNOWN (empty).
As for DB examples see:
<A
href="">http://msdn.microsoft.com/library/default.asp?url="";>
AB 4.29.8 features new function Nz
<A
href="">http://www.amibroker.com/guide/afl/afl_view.php?name=NZ
that allows to easily convert Null (empty) to
zero:
Nz( Foreign("RATL","O") ) + Nz( Foreign("CSCO","O")
)
Best regards,Tomasz
Janeczkoamibroker.com
<BLOCKQUOTE
>
----- Original Message -----
<DIV
>From:
Dimitris
Tsokakis
To: <A title=amibroker@xxxxxxxxxxxxxxx
href="">amibroker@xxxxxxxxxxxxxxx
Sent: Thursday, March 06, 2003 11:37
AM
Subject: [amibroker] Some strange
addition rules
I noticed that
{empty}+X={empty}
X+{empty}={empty}
One should expect {empty}+X=X.
Consequently, special care should be taken with similar
additions [or subtractions, multiplications, divisions]
If you try to add Foreign("RATL","O")+Foreign("CSCO","O")
and the RATL data is missing for a certain bar, the result would be
{empty}
instead of the expected Foreign("CSCO","O")
Dimitris TsokakisSend
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