The trend array is not exactly the same thing as the Erl variable being trended. You don’t set values in the actual trend array yourself, EMS does it for you at the end of the zone timestep. The bump doesn’t occur until the end of the zone timestep and is not associated with any Erl program execution. It occurs right after the calling point EndOfZoneTimestepAfterZoneReporting has executed.
If you want to retrieve the value for the current timestep, use the native Erl value being trended instead of the trend itself.
When accessing the trend, the index 1 is for the previous zone timestep, the first historical value. Zero index is not going to work.
If I assign a value to the trend variable array, like so:
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