I have a field in a webmap called 'deviceId' that displays a unique string for each device that pushes data into it.
Ideally, I want a widget in an Operations Dashboard that displays a count of the number of unique devices.
I can see how to display a count of features, but can't see how to create a query that filters by unique value.
In a round-a-bout way, a bar graph achieves something similar, by displaying a unique bar for each deviceId with counts of the number of features for that deviceId, but it's not the effect I want. I just need a single count figure.