CALCARCHEXPR action

Function
The action performs a calculation of specific archival expression in relation to archival values. Archival values are presented through the names of archival objects in expression.
Declaration

CALCARCHEXPR archExprIdent_Txt, btIdent_TimA, etIdent_TimA, stepIdent_Int, _ignoreInvalid_Bool, _locVarColValueIdent_Rec, statusIdent_Int


Parameters
archExprIdent_Txt in Value identifier of Text type containing the expression.
btIdent_TimA in Identifier of AbsTime type - interval beginning.
etIdent_TimA in Identifier of AbsTime type - interval end.
stepIdent_Int in Identifier of Int type - time step [s].
_ignoreInvalid_Bool in Identifier of Bool type - invalid values in expression will be replaced by 0.
_locVarColValueIdent_Rec out Reference to local variable column of RECORD type - final values.
statusIdent_Int out Identifier of Int type - success of calculation.

Description
The action performs a calculation of specific archival expression in relation to archival values. Archival values are presented through the names of archival objects in expression.

The rules of this calculation are identical with calculation mentioned in definition of calculated archival object.

In case of using the structured archive in expression, a zero [0] number of row cannot be used.

The calculation is performed for entered time period <btIdent_TimA, etIdent_TimA.

If parameter stepIdent_Int
= 0 - it means the calculation for change => each change some of the source data (archived) causes the entered expression recount and relevant value will be in result. ≠ 0 - it means the periodic calculation => the entered expression is evaluated in periods btIdent_TimA, btIdent_TimA+1*stepIdent_Int, btIdent_TimA+2*stepIdent_Int .... Resultant value array is written into entered column of local structured variable _locVarColValueIdent_Rec (variable can be dimensioned again).
Note
1. The expression must contain the name at least one of archive value.
2. If expression contains several archive values, they all must have one parent in terms of DODM.
Example
 TIME _bt, _et
 INT _step
 INT _retCode
 TEXT  _expr
 TEXT _err
 BOOL _bIgnoreInvalid
 RECORD NOALIAS (SD.Data) _data
 
 _bt := %StrToTime("00:00:00 01-01-2008")
 _et := %StrToTime("00:00:00 02-01-2008")
 _step := 1
 _bIgnoreInvalid :=  @TRUE
 _expr :=  "H.a + H.GetArchRowCol_Ref[2]^I2 + H.GetArchRowCol_Ref_Col_I1[2]"
 
 CALCARCHEXPR _expr, _bt, _et, _step, _bIgnoreInvalid, _data^Value, _retCode
  
 IF _retCode =  _ERR_NO_ERROR THEN
   ; processing of result
 ELSE
   _err :=  _ERR_MSG ; extended error description
 ENDIF

Owing to the expression parsing works during system running (not during configuration) and if some error occurs, it is possible to obtain its detail description as value of predefined local variable of Text type _ERR_MSG.

Related pages:

Script actions

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