I have the following pivot table:
Each row represent a specific state. The states are grouped. Each column is a timestamp.
Let's take the group "operational_status". At 09:52:30.273 the operational state changed to converter, isolation_monitor and safety_relay. And at 09:52:39.784 the state changed again to converter and safety_relay.
Now I want to have the first state change for each timestamp until the next state change and so on. For that example I want to have the first state (converter, isolation_monitor and safety_relay) for each red marked column.