reducer.join.nonnull
reducerAlias of reducer.join.forbid-nulls
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The 'reducer.join.nonnull' function outputs for each tick of Geo Time Series™ which are in the same equivalence class, the concatenation of the string representation of values separated by the join string.
The location and elevation returned are from the latest measure.
It will return null for any tick where one or more GTS have null values.