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PmTrend - Deatiled object description

See: Object PmTrend
 
For detailed description of creating trends see PROMOTIC Coursebook - chapter Trends. For the examples see Example of creating client/server trends.
 
Any number of variables can be trended (i.e. stored on the 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 1.variable, the value of the 2.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 Intranet/Internet by the configuration of the Web Server page. It is necessary to use the PmWeb object for providing the data into the web (also possibly the PmWebFolder configured for trends). The client requiring data from this WEB component is type of "PmWebClient" from the license 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.

By the SetValueByTime method it is possible to edit the stored data backward (overwrite originally stored values).

 
The PmTrend object can dynamically change the location of the data archive on the disc, or connect to existing data archive using the Open and Close methods.
 
The PmTrend 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: PmTrend object in "Read only (new records can't be written)" mode.
 
#vars identifier:

In the PmTrend object, the #vars identifier is used in order to enable the access to the data items (of the Var type) defined on the Data page. This identifier can be used in methods working with application object tree (e.g. for the Pm method), or for the PP binding in the application and in panels. For example, the pMe.Pm("trend1/#vars/aaa") method returns the aaa data item from the object named trend1 that is of the PmTrend type.

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