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 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 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
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).
object can dynamically change the location
of the data archive on the disc, or connect to existing data archive using the Open
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 cannot be written)" mode
In the PmTrend object, the #vars identifier is used in order to enable the access to the variables (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 variable from the object named trend1 that is of the PmTrend type.