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PmaTrendGroup - Deatiled object description

See: the PmaTrendGroup object.

For detailed description of creating trends see PROMOTIC Coursebook - chapter Trends.

Any number of variables can be trended (i.e. stored to disk and into the memory). These variables are stored as records with the following information: the store time, the system attribute, the value of the 1st variable, the value of the 2nd variable, etc. When halting and re-starting the application the storing continues in the existing file (in the database, in the binary file) at the point of the last stored record.

The stored data can be provided into the Internet/Intranet by the configuration of the "Web server" tab. It is necessary to to use the PmaWeb object for providing the data into the Web. The client requiring data from this Web component is of the PmWebClient type from the licence point of view.

The data (stored by this object) can be obtained by the GetData and GetValueByTime methods. The GetData method also allows to filter the data according to their values and it also provides the basic statistical functions (average, minimum, maximum, sum, count) that can be performed over all or only the filtered data.
It is possible to edit the stored data backward (overwrite originally stored values) by the SetValueByTime method.

The PmaTrendGroup object can dynamically change the location of the data archive on the disk, or connect to existing data archive using the Open and Close methods.

The PmaTrendGroup object does not have to create the trends. It can also be switched to a "read only" mode and offer the trends in files created by another systems. See: The PmaTrendGroup object in "Read only (new records cannot be written)" mode.

#vars identifier:
In the PmaTrendGroup object, the #vars identifier is used in order to enable the access to the variables (of the PmVar type) defined on the "Data" tab. This identifier can be used e.g. in the Pm method, or for the PP data binding in the application and in panels. For example the method pMe.Pm("trend1/#vars/aaa") returns the aaa variable from the object named "trend1" that is of the PmaTrendGroup type.
See also:
- PmgTrendViewer (object)
- PmVar (object)
- ExtTrend (object)
PROMOTIC 9.0.17 SCADA system documentation - MICROSYS, spol. s r.o.

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