5 Replies Latest reply on Nov 25, 2013 1:20 PM by cmanhard

    Interpolation of 2D AF Tables


      Hello there,


      We are in the process of moving from an old system to AF for one of our customers. That old system also contains 2D correlation tables which are used to calculate the density for one of their products.


      In that particular system they simply input the X and Y value (temperature and pressure) and the density rolls out. So there are three columns to the table namely: X, Y and Result


      I imported the 2D table into AF but I don't see how I can interpolate since two interpolation calls don't seem to be allowed in one formula.


      Am I missing something? Or does anyone have any suggestions as to how I could tackle this?




      P.S. If this post is not in the right place then feel free to move it. I really couldn't find a better place ;)

        • Re: Interpolation of 2D AF Tables

          Hello Vincent,


          Currently, as far as I know, there isn't possible to do this without some custom development. Some time ago we've developed a custom AF Data Reference (as I remember, even for AF 1.x) to do similar task. You can follow this way or wait for OSIsoft to implement it in furure version of AF (1D interpolation is already on its way to release).

            • Re: Interpolation of 2D AF Tables

              Hello Sergey,


              Thanks for your reply. Is that custom AF DR still around somewhere? Or is it not compatible with the current version of AF?

                • Re: Interpolation of 2D AF Tables



                  Is your need restricted to linear interpolation of X and Y or do you have a need for a curve fit?  (e.g. curve fit the Y values using a quadratic or even higher order polynomials)

                    • Re: Interpolation of 2D AF Tables

                      Hello Steve,


                      Thank you for response.


                      Linear interpolation should suffice for our usecase. Is AF capable of doing that out-of-the-box? Or is there a custom AF DR available?

                        • Re: Interpolation of 2D AF Tables

                          AF does not have a 2D Interpolation function in the Table Lookup DR, nor am I aware of a custom DR.  You can create one using the existing Table Lookup combined with Formula, but it is not pretty.  It takes 8 table lookups and 3 formulas. With the upcoming Abacus, scheduling the final calculation as a PE would ensure the data is up-to-date with less impact on the clients as they would not need to re-execute the 8 table lookups.


                              Table has columns, x, y, and R.


                              Attributes X and Y are the inputs, Attribute R is the Result


                              X.Min and X.Max are the bounding values of input X in the table's x column


                              Y.Min and Y.Max are the bounding values of input Y in the table y column


                              R1-R4 are the 4-corner results in the table which bound the result


                              RA and RB are used in the final calculation of R