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HI , wj takes the initial value within the window to be the prevailing values that existed before the window started.
So for example in the case of tempBackRight for the second time interval between 12:02:56.325 and 12:03:33.564:
- you are correct there is no event between this time for tempBackRight
- wj will take the prevailing value that existed before the window started i.e. 20.87774 which happens to be the only entry for this sensor.
- This is a useful feature of wj because we would rather have the last known value over a table with a lot of nulls
Note that if we did want to consider the values that only occurred during the window, we could use wj1. Hope that helps. It is correct in this example to not have lapId as a column to join, the laps are represented already by the time and endTime values defining the lap window.
If you’re still getting an error you can share your attempt with a spoiler tag and I can better help with where you might be going wrong.
Thanks,
Michaela