3 Replies Latest reply on Mar 1, 2012 3:31 PM by mhamel

    Calculations on Historic data


      We are dealing with future data in a certain project we are working on. So in order to save the future data in PI, we are back dataing it and saving it to PI.


      The issue, we are having is performing calculations on this data.


      My understanding is that we can not use PE on historic data. Any suggestions?


      Is it something that we can achive by using PI ACE or PI event frames. I am not familiar with either of the technologies.


      Thanks for your help.



        • Re: Calculations on Historic data

          By historical data are you performing an actual vs predicted type of calculation?  PE has a PrevEvent function that can access historical data...really depends on the type of calculations, and volume of calculations you need to perform when considering PE, ACE, ...


          For example, let us assume you stored future data with a 1 day offset to a corresponding PI Point.  Your comparison PE could be something like:


          if 'ActualTag' = PrevEvent('PredictedTag','*-1d') then "WeGotItRight" else "WeGuessedWrong"


          Check out PIPC\Help\PEReference.chm help file for all the functions available.

            • Re: Calculations on Historic data

              Another usefull PE Function to take a look in the documentation that Rhys recommended is  TagVal(tagname [, time]).

                • Re: Calculations on Historic data

                  @Keerthi: We have presented at the last vCampus Live! 2011 a hands-out session on how to apply future data in the PI System. If you missed it, you can download the material from the Download section of vCampus under the category Extras and the name is vCampus Live hands on sessions.


                  The hints you will find inside this document will let you use all analytical tools of the PI System (PI ACE, Performance Equation or PE, Totalizer, PI AF Formula, etc.) to compare actual and predicted values.


                  If you want to learn more on PI ACE, I suggest you take time to watch a previous Builders Café Webinar from the (PI ACE 2010 R2 in Action) on the topic which you can find here.


                  On PI Event Frames, I suggest this other Builders Café Webinar (PI Events Frames - Find your data by events) which you can find here.


                  The example provided by Rhys on PE is also valid for a simple comparison. I suggest utilizing YouTube as a fast way to learn Performance Equation by browsing the link here.