GroveStreams

Derivations - current period474

ctmorrison private msg quote post Address this user
In order to save data (communications), I've been sending readings from my devices as long strings (ex. 0734|0801|-990|-990|-990|-990) and then extracting the desired reading and dividing by 10 and storing the result in a float. This seemingly worked for a long time. However, at some point in time in the not too distant past, I was required to specify a function in the derivation when I referenced the string stream. It seemed natural to specify "Last" so I got the last reading.

I've just run into some situations where the last reading is actually several days old, but I really only want the reading from the current period. I see I can specify a base period on a String, which surprised me and I'm now hoping that will result in the derivation that uses the string to use the current period, but I'd like confirmation this will perform as expected.

On my many dashboards, I turn digital widgets white based upon latency. Therefore, knowing the derived values are missing is important.
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MikeMills private msg quote post Address this user
Quote:
Originally Posted by ctmorrison
I can specify a base period on a String
- This should work for an dependent Interval Stream.
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ctmorrison private msg quote post Address this user
I assume I cannot change a Stream into an Interval Stream. Correct? I believe I started using Stream not recognizing this consequence.
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MikeMills private msg quote post Address this user
Quote:
Originally Posted by ctmorrison
I really only want the reading from the current period
- What do you mean by this? What is the current period? Is it the current cycle of the stream being derived? Is it the last value of the dependent stream?
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ctmorrison private msg quote post Address this user
Sorry -- forgot all about this. What I want is the current cycle of the stream being derived. I'm trying to use the "latency" feature of the digital widgets and turn them white and set them to zero when the data is more than 30 minutes old. I've done this countless times in the past, but I may have switched from Interval Streams to Streams without understanding this impact.
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