How can we improve PI DataLink?

Compressed Data and Tables

Compressed Data should be able to (or have the option to) query multiple tags and return the results as a single table/array of information, instead of independent columns of data. Returning independent columns of data results in rows being mismatched across multiple columns because of missing events. A table should be able to be easily created that keeps the data from multiple tags contextualized with each other based on the time stamps.

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  • volljm commented  ·   ·  Flag as inappropriate

    I was not referring tables in reference to Excel Tables as the specific object, I was more referring to a general 2-dimensional table of data, a matrix of data.

    A table of data would be multiple tags where the values from these multiple tags are associated/related to each other based on a common timestamp. This information can be retrieved into a 'table' like format using multiple datalink functions, typically a combination of Compressed Data and Timed Data (using exact time due to not wanting to accidentally interpolate for data missing). The issue is the inability to utilize a single Datalink function.

    Using a single Timed Data function across multiple tags is only possible with knowledge of the expected timestamps, which is not always possible . . . usually not possible. Using a single Compressed Data function will give incorrect results because of any missing values on one or more tags . . . the rows will become mismatched from each other.

    Thus retrieving this data into Excel ends up being much more complicated and fraught with pitfalls and traps for any users that have not given very careful consideration of the data structure and the exact behavior of datalink functions . . . and i say that based on experience of having many users having issues in this specific area.

  • AdminJeremy Roberts (Sr. Product Support Engineer, Visualization, OSIsoft) commented  ·   ·  Flag as inappropriate

    Hi James,
    Excel does not allow multi-cell array formulas in tables, so it is not possible for Compressed Data to be changed to fulfill your request. (seen if you attempt to make a table out of Compressed Data cells, you will get the message "Multi-cell array formulas aren't allowed in tables.")

    So a new DataLink function returning something other than multi-cell array formulas would be required. That would be a nontrivial effort, so we would really like to get a better understanding of your use case.

    What is your end goal for this functionality? (use in a chart, report, PivotTable/PivotChart, a business integration with Excel, etc.)

    You mention "data from multiple tags contextualized with each other based on the time stamps." Something along those lines can be accomplished using multiple Archive Value or Timed Data calls, for exact archive data or interpolated values. Can you please clarify the additional functionality you're requesting? Thanks!

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