reducer.argmax is available since version 1.0.11.
reducer.argmax function outputs for each tick, the tick and the concatenation separated by ‘,’ of the values of the labels for which the
value is the maximum of Geo Time Series™ which are in the same equivalence class.
It operates on LONG and DOUBLE.
There is no location and elevation returned.
This reducer takes an additional LONG parameter to choose the maximum to report (use 0 to report all), and a STRING parameter to choose on which label it operates.