Interpolated values

Many PI DataLink functions can return interpolated values which are useful for PI points associated with time stamps. For example, when you select Archive Value function in DataLink, you will see the options pane on the right-hand side of the spreadsheet as shown below. Selecting Retrieval mode of interpolated will return an interpolated value at the time stamp you specify, y in the below example, rather than the last recorded value that precedes the time stamp. Note that auto mode also returns interpolated value for numerical tags.The interpolated value depends on the time stamps of the recorded values.

• For time stamps before the first recorded value, the function returns either Pt Created or No Data.

• For time stamps between two recorded values, the function determines the value at the time stamp using linear interpolation between the recorded values. For points that store discrete values, such as digital state points or step points, the function returns the last recorded value that precedes the time stamp.

• For time stamps after the last recorded value, the returned value depends on the point type:

  • For historical PI points, the function returns the most recent value.

  • For future PI points, the function returns No Data.